The live-action Sonic the Hedgehog movie was originally slated to be released sometime in November 2019, but was delayed to February 14th, 2020 as a result of the reception to the film's debut trailer released on April 30th, 2019. The main cause of the backlash being that the film was planned to feature a humanoid redesign of Sonic that was so negatively received by fans and audiences alike that the film's team hired artist Tyson Hesse, who had previous experience with the Sonic franchise, to make a more visually appealing redesign for the final movie that was more positively received and incorporated into all previously-released film footage.

Before the singular story concept of Sonic fighting against Dr. Robotnik, Sonic's character development was very different. During the 2018 Game Developers Conference, game designer Hirokazu Yasuhara and character designer Naoto Ohshima revealed that the series almost had connections to World War II.

"Sonic" was originally going to be a fighter pilot who earned the nickname "hedgehog" because of how his hair stood up while flying his plane at high speeds, while the Sonic the Hedgehog design known today was merely a nose decal on the front of his plane. The details of his time in the war were then re-imagined as a children's picture book by the pilot's wife. She took the Sonic the Hedgehog design and based it on her war veteran husband, making the game a story within a story. American pilot Chuck Yeager, the first pilot to break the speed of sound, was also mentioned in Yasuhara and Ohshima's pitch summary.

Additionally, they showed off line art for a proposed dance sequence during the game, originally intending for Sonic to be a trendy dancer, but this along with the meta-story elements were scrapped during development.

In the third installment of the Untold History of Japanese Game Developers book series released in 2018, Ohshima reiterated that Sonic was going to be a human boy, but SEGA rejected the design, not wanting their mascot to be a human, and Ohshima admitted that he does not have any concept art of Sonic as a human due to his proposal just being a basic outline. Despite this rejection, the core layout of Sonic the Hedgehog's speed-based gameplay and map design was set in stone by this time.

In an interview, Naoto Oshima was asked if the blue birds were a direct reference to the game Flicky. Oshima said yes, and also mentioned that he asked game's designer Yoji Ishii's permission to use Flickies in his work.

In 2012, Ken Balough announced that Big the Cat would be retired from the franchise for the time being as they could not find a good use for the character, and all things that they already tried didn't work out for him. This however did not stop Big from making cameo appearances in Sonic & All-Stars Racing Transformed, having a trophy in the 3DS version of Super Smash Bros. 4, and being playable in Sonic Runners. Big was eventually reintroduced to the mainline Sonic games in Sonic Frontiers.

There was almost going to be a Sonic game based on skateboarding made for the Xbox, GameCube, and PlayStation 2 called Sonic Xtreme (not to be confused with the cancelled Sega Saturn game of the same name). This game was developed by a San Diego company called Vision Scape Interactive.

Development began in 2003 shortly after Vision Scape finished up Bare Knuckled Grind. The game was initially planned to be ported to other consoles. There were also going to other skateboarding games using the same engine, but with different intellectual properties, including the Nickelodeon TV show Rocket Power. Unfortunately, budget issues is what resulted in all 13 projects cancelled. They later worked on cutscene animations for Sonic Heroes, and later pitched to Sega the Sonic X-Treme prototype.

The prototype was finished in a week, and originally had planned to use hoverboards. The player would be to race against Sonic or Shadow. Yuji Naka, former head of SEGA, was impressed at the time and asked Vision Scape to make design documents for the game. However, when they did show the documents to SEGA, they went silent.

Later on, in September 2005, Sonic Riders was announced. People at Vision Scape believed that SEGA took some of the concept from Sonic X-Treme. and used it for Sonic Runners. However, legal issues from SEGA forced Vision Scape to shut down in 2006.

As a result of a sponsorship deal between the motor racing circuit Donington Park in Leicestershire, England and SEGA, the 1993 European Grand Prix was adorned with SEGA logos. Even the race itself was renamed the SEGA European Grand Prix.

Ayrton Senna won the rain-drenched event after passing four cars on the first lap and holding off his teammate Alain Prost through the race's length, and was presented a trophy which featured Sonic the Hedgehog. While the image of Senna holding this trophy was widely circulated around the Internet, it was unfortunately only a fake trophy used for a photo op. It's unknown what became of the Sonic trophy.

At E3 2004, SEGA displayed a tech demo of Sonic the Hedgehog for the Nintendo DS simply named 'Sonic DS'. The game played by swiping back and forth on the bottom touch screen to allow Sonic to gain speed.

There exists an unlicensed recreation of Sonic the Hedgehog for the NES called Somari, featuring Mario running through most of the levels found in Sonic 1. As infamous as the game is by itself, there are various "official" and even "unofficial" versions of it, usually replacing Mario with Sonic.

Silver the Hedgehog was originally going to be an orange mink named Venice, but the developers decided against it and changed him into a hedgehog as they didn't think that a mink would fit in with the other characters.

Tomoya Ohtani, a recurring composer for the series, frequently samples a portion of the famous drum break from the song Amen, Brother by The Winstons. This portion can be heard in 'Vs. Orcan' and 'Skullian' from Sonic Colors, the extra boss theme 'Boss - Big Swell' from Sonic Rush Adventure, and 'Cool Edge Day' from Sonic Unleashed, just to name a few.

Since Sonic was very popular in English speaking countries, one of Sonic's quirks in Japan (performed by Junichi Kanemaru) is that he may speak English at times, unlike other characters.

Andrew Rannells, the award-winning actor who played the lead character Elder Price in the play The Book of Mormon, was the voice director for the English dub of Sonic X. He played characters such as Bokkun, Decoe, Gamma, and Mr. Stewart. He also played the G.U.N. agents in the game Shadow The Hedgehog. Rannells actually worked on quite a few 4Kids shows during his time there, including Pokémon, Pokémon Chronicles, Kirby: Right Back At Ya!, F-Zero GP Legend, and voiced characters in 4Kids-acted games in the Yu-Gi-Oh and One Piece series.

The US Sonic Heroes manual states that Doctor Eggman is a feminist. This was added during localization and did not appear in the Japanese manual.

Sticks the Badger from the Sonic Boom sub-series resembles Aika from Skies of Arcadia, another Sega game. Both Sticks and Aika use a boomerang as their weapon of choice, have nearly identical hairstyles and have orange as one of the predominant colors in their design.

According to the Archie comics, Sonic the Hedgehog's real name was originally "Olgilvie Maurice Hedgehog", and was meant to act as a part of a never-used plot. However, due to one of the comic writers leaving the staff, this concept was never touched upon, and was eventually retconned as Sonic legally changing his name at an early age, leaving his actual first name a mystery.

Fang the Sniper, called Nack the Weasel in the English release of Sonic Triple Trouble and various English-language comic books, originally wielded a realistic gun. However, this was considered too violent for the Sonic series, and was changed to a cork-shooting popgun during development of his debut game, Sonic Triple Trouble.

According to the Sonic Comic series, Sonic's speed and color are a result of a lab accident, which involved a hamster wheel and some sneakers. This somehow gave him blue fur and super speed. Sonic was supposedly a normal brown hedgehog until this accident took place.

The skid noise made when Sonic stops running comes from Out Run, an earlier SEGA game.

Dr. Robotnik was created to be the opposite of Sonic, and to be the bad guy. During the development of the game, there was a growing debate between developers and environmentalists, and Robotnik was created to represent machinery and development, as apposed to Sonic, who represented the environment.

His egg shaped redesign came from Naoto ÅŒshima wanting to give the characters designs that were easy enough for kids to draw.

The design for Dr. Robotnik/Dr. Eggman was based on a caricature of Theodore Roosevelt in pajamas.

In all of the Sonic Riders games, there is a gear titled "The Crazy", which resembles a taxi. This is most likely a reference to another SEGA series, Crazy Taxi.

Tails' real name, Miles Prower, is a pun on "miles per hour", a reference to Sonic's speed.

There is a series of posters in several Sonic games advertising a movie series called "Chao in Space". These posters also feature the names of various Sonic characters.

The trademark Sonic Emblem, as featured in Sonic the Hedgehog and subsequent installments on the Sega Genesis, is based off of the logo from the 1988 Sega arcade title, Wonder Boy III: Monster Lair.

In the early Sonic games, The Chaos Emeralds appeared to be 'Emerald Cut'. Eventually, the emeralds in the series became 'Brilliant Cut'. In reality they should now be Chaos Diamonds, as a brilliant cut is reserved for diamonds.

In the 1990 arcade racing game Rad Mobile, there is an air freshener of Sonic that is hanging from the rear-view mirror. This marks the first time Sonic has ever made an appearance in a video game, which, interestingly enough, predates the release of Sonic the Hedgehog in 1991.

In Sonic the Comic, Issue 71, it is revealed that Sonic is responsible for "Creating the most vicious dictator on Mobius" by tripping Dr. Robotnik with a wire, combining a rotten egg with the evil of the Chaos Emeralds.

In "Sonic the Comic, issue #8, The Origins Of Sonic," Sonic was originally brown and very spiky. He had met Dr. Ivo Robotnik (known at the time as Dr. Ovi Kintobor) by finding his lab, and they had become friends. Dr. Kintobor performed experiments on Sonic's super speed, which helped him to run even faster, and with the aid of the Power Sneakers Dr Kintobor invented, it allowed him to run so fast that he broke the sound barrier, turning him into a more familiar blue form.

In 2008, the series was awarded the Guinness World Record for the "longest-running comic series based on a video game". Archie Comics' run of Sonic the Hedgehog lasted from 1992 to 2016, resulting in the publication of 290 issues (including specials) over the course of 24 years.

In 1993, Sonic the Hedgehog became the first video game character to appear as a balloon in the Macy's Thanksgiving Day Parade. The balloon popped on it's one and only flight by being pushed into a lamp post by strong gusts of wind, hurting a kid and a police officer on it's descent. Because of this incident, the balloon was retired.

A second Sonic balloon based on his modern redesign was used between 2011 and 2013 to celebrate the series' 20th anniversary, and was brought back one more time in 2021 in accordance with the series' 30th anniversary.

Sonic's favorite food is chili dogs. This trait was first introduced in the 1993 animated series "Adventures of Sonic the Hedgehog" and was later officially incorporated into the video game series starting with Sonic Chronicles: The Dark Brotherhood.

In 2010, SEGA de-listed every single Sonic game with anything less than an average Metacritic score so that they could not be bought new at retail or downloaded from console-based online services. This was in order to increase the value of the franchise to prepare for a "comeback". Ironically, Sonic Free Riders, released the very same year, has a below-average Metacritic score of 47 out of 100.

Sonic was originally planned to have a human girlfriend called Madonna. She would chase Sonic around, similar to how Amy Rose acts in later games.

Sonic's shoes were inspired by Michael Jackson's boots and the color scheme of Santa Claus. Sonic's personality was inspired by Bill Clinton.

There are at least two cases of art plagiarized from deviantart.com appearing in Sonic games. A piece of art of Sonia was mistakenly added to Sonic & Sega All-Stars Racing, and some fanart that was made for a Sonic and the Black Knight contest turned out to be a replica of someone else's artwork. Sega apologized both times.

The human body has a Gene called "Sonic Hedgehog", named after the character. The gene has an inhibitor (something that stop the process of a gene) named "Robotnikinin", named after Sonic's Nemesis, Dr. Ivo "Eggman" Robotnik.