In the Coffee Shop during the "Free the Sperm Whales" mission, heading into the bathroom, clicking the foot icon on all 3 screws on the broken mirror and then clicking the foot icon on the skull drawn on the side of a stall will trigger a secret cutscene. Butt-Head will pull out a shotgun, say "$&*@ You Beavis" and shoot Beavis in the head.

Mirroring a similar easter egg on the Temple stage, the Sheikah text on a platform in the Great Plateau Tower stage says "SMASHBROS" twice.

In the NES version, there are unused sprites suggesting that Spider-Man was once planned to climb walls.

By breathing fire into one of the Tiki statues of the level Tiki Tropics, the sound that Aku Aku from the Crash Bandicoot series makes when breaking open an Aku Aku Crate will play.

According to Sakurai's Famitsu column, he chose to build the game off of the previous entry's mechanics instead of building the game from scratch as choosing the later would have caused a large portion of the game's roster to be cut. This would be due to the fact that more time would have had to be put into rebuilding each individual character.
He also remarked this decision allowed for more focus to be put on other aspects of the game.

In an interview, art director Yasushi Yamaguchi was asked about how his team came up with the idea of having 2-players, he commented:

"The development of Sonic 2 was informed by two factors: the things we couldn’t do in the first game, and the response/feedback from players. The idea of controlling Tails came from programmer Yuji Naka, who wanted a kind of “1.5 player” game—something where it would be ok if the second player died. He wanted to allow for a tandem experience where both skilled and unskilled players could enjoy the game together."

In the Japanese version, by pressing A,B,C,A,B,C,A,B,C in rapid succession on the Options screen, an easy mode will be unlocked. The game will be significantly easier, but the first level of the game will change to a light and cheery aesthetic instead of the dark and moody one of other difficulties.

At the north end of the Bridge map, using the "Kangaroo on Command" power up will allow the player to scale the rock wall border of the map and enter a secret room. Upon entering the room, a message will state "Friggin Kangaroo on Command freak." Turning around from that message will show another large message that says "Now you are stuck SUCKER" and create an invisible wall that will trap the player in the secret tunnel.

If the game detects a pirated copy, this message will appear upon booting up:

ALERT!!!

Pirated Copy!

But you're in luck. For
just $32.50 you can get
your own, unpirated copy
of 3-K Trivia!

Unused Paintinator models and icon can be found in the data.

In Route C, if the player talks to Jackass after the bunker's destruction, she'll comment that she had a friend on The Bunker named "White." This friend is revealed to be The Commander in the Black Box Edition Art Book.

In the RC Car play section, the numbers 1889 and 2018 can be found under the cover of the controls. "2018" represents the year that Nintendo Labo released and "1889" refers to the year that Nintendo started as a company.

Once you've finished the game and return to the main menu, Spoiler: when Chloe, the android who serves as a guide, asks you if she could be set free, it was originally intended that she'd permanently disappear if the player lets her go. However due to player requests, in an update it was made that if the player had let her go, they could later be asked if they wanted another Chloe android to take her place.

During the Rupert the Gunsmith sub-mission, a pink teddy bear can be found in Rupert's apartment. Activating this bear will make it say "I love you.". As the player continues to activate this bear, the bear's dialogue will change, and it will insist you stop touching it. If you proceed to activate it after this warning, its eyes will turn red, and the bear will explode.

Super Smash Bros. Ultimate is the first game in the series that requires players to select a stage before selecting a character in multiplayer matches. In previous entries, as is common in other fighting games, it was the opposite. This is an attempt by Masahiro Sakurai to change up the strategy of the game (specifically stage-character match-ups).

The cartridge label of the NES game Ice Climber found in the game's main treasures differs in it's appearance depending on what version is being played. In the japanese version it uses the Famicom appearance and artwork, whilst in the western version it uses the NES appearance and artwork.

There is code from Battlezone II: Combat Commander, another game developed by Pandemic Studios, left in the GameCube version's files.

According to Tetsuya Nomura, the aesthetic and environment design for part of the Hercules-based "Olympus" world was primarily inspired by California's Yosemite National Park, despite, story-wise, taking place in Ancient Greece. This decision came about when co-director Tai Yasue had visited the real-world location.

In the Wii version’s files is an unused animated version of the EA Sports logo. The final game uses a stationary one.