As of Super Smash Bros. Ultimate in 2018, Shadow the Hedgehog is the only third-party Assist Trophy to appear in every Super Smash Bros. game since the introduction of Assist Trophies in Super Smash Bros. Brawl in 2008.

As of Super Smash Bros. Ultimate in 2018, only three characters that started out as Assist Trophies became playable in future installments:

•Little Mac, an Assist Trophy in Brawl, then became playable in Super Smash Bros. for 3DS/Wii U
•Dark Samus, an Assist Trophy in Super Smash Bros. for 3DS/Wii U, then became playable in Ultimate
•Isabelle, an Assist Trophy in Super Smash Bros. for 3DS/Wii U, then became playable in Ultimate.

Sephiroth's inclusion as a DLC fighter was apparently so top secret that even certain members of Square Enix had not known that the villain was going to be included in Super Smash Bros. Ultimate until the corresponding show-stealing announcement at The Game Awards 2020 was made. Even Square Enix employee and Final Fantasy VII Rebirth director Naoki Hamaguchi was quite shocked and stated:

When it was announced that Nickelodeon All-Star Brawl's paid DLC characters were due to be revealed, it was with a tweet reading "Back to the lab again". Some theorized this was a tease for either Jimmy Neutron or Jenny Wakeman, both highly-requested characters with a technology theme. However, this seems to actually be a reference to a livestream by Super Smash Bros. Ultimate YouTuber GimR from two days earlier. GimR advertised the livestream for days prior, promising a new technique that would change the game's competitive scene, only to fail to actually start the stream due to technical issues. During the time he was live, he played a looping intermission animation depicting him as Dexter from the Cartoon Network series Dexter's Laboratory and playing the song "Back to the Lab" by Prince Paul and Wordsworth for over an hour. This mistake would become a meme within the Super Smash Bros. community for a short while afterwards. Ultimately, Jenny, Rocko and Hugh Neutron, the latter two not being related to technology, were revealed, and GimR would separately reveal the promised new technique, the "Slingshot", two days after the failed livestream.

In the Japanese version of Super Smash Bros. Ultimate, Banjo & Kazooie's down special, Rear Egg, is called おケツタマゴ (Oketsu Tamago), which in English directly translates to "Ass Egg". This particular name was utilized for the Japanese localization of Banjo-Kazooie, at least its Japanese website.

It's worth pointing out that, in the English version of Banjo-Kazooie and Banjo-Tooie, this move has no name, as it's rolled into Egg Firing as one ability. However, internally in both games, the animation is indeed named "egg ass", which the Japanese version literally translates for its name.

The Breegull Bash move in the Japanese versions of Banjo-Tooie and as well as Super Smash Bros. Ultimate is called ハリセンカズーイ(Harisen Kazui), which literally translated into English is "Slapping Fan Kazooie". A harisen is a giant paper fan that is typically used as part of a manzai act, where the straight man smacks the funny man in response to their jokes or foolishness. The "Fan" item that appeared in Super Smash Bros., Super Smash Bros. Melee, and Super Smash Bros. Brawl is actually a harisen, and it's even called as such (はりせん) in the Japanese version of those games as well.

It's worth pointing out that in general, the Japanese localizations for the Banjo-Kazooie games seem to exclude any mention of the word "Breegull", the name of Kazooie's species. This is something Masahiro Sakurai made note of when showcasing Banjo & Kazooie's moveset in Super Smash Bros. Ultimate.

King K. Rool's render pose in Super Smash Bros. Ultimate seems to be lifted from an unused character select screen render for Zelda in Super Smash Bros. Melee.

Joker from Persona 5 was announced as the first Fighter's Pass DLC character for Super Smash Bros. Ultimate at The Game Awards 2018 on December 6th, 2018. This means that while he was technically the only Fighter's Pass DLC character to be announced before the release of Super Smash Bros. Ultimate, it was only a few hours before December 7th when the game was released.

During the pre-release of Super Smash Bros. Ultimate, there was a minor controversy involving the character of Waluigi, a long-time fan-requested character who had been announced as an Assist Trophy (rendering him a non-playable character) early in the game's pre-launch cycle. This controversy entailed Super Smash Bros. creator Masahiro Sakurai supposedly being harassed en masse by Waluigi fans with inappropriate memes, requiring him to block the offending users - this was picked up by many gaming news sites, usually with the sources being unsourced tweets from random users, and became a hot topic in Smash speculation with some speculating that Waluigi would be blacklisted from appearing in any Smash game from that point as a bizarre form of retribution.

Further investigation into this, however, shows that there are only 2 known tweets that fall under the category of "inappropriate memes" that had gained users blocks - one depicting Sakurai in front of the September 11th attacks on the Twin Towers and another depicting him as Adolf Hitler, both with extremely low interaction rates and content that, while certainly detestable, had its quantity exaggerated beyond reason and is not a rare or unusual occurrence for game developers. Additionally, Sakurai has been known to block Twitter users for anything that he finds strange, even if it isn't actually offensive or related to Smash requests, such as a thread of users playing tic-tac-toe on an edited image of Persona 5 character Haru's forehead.

The first Aparoid boss of Star Fox: Assault is a giant butterfly looking creature that appears at the end of the Fortuna mission. This particular Aparoid would reappear as a trophy in Super Smash Bros. for Wii U and also a spirit in Super Smash Bros. Ultimate, in both cases being dubbed simply as just "Aparoid".

The official Japanese Star Fox: Assault guidebook reveals this type of Aparoid to have a proper name: ゼグダリア (Zegudaria), or Zegdahlia as it's called by the provided English text.

In 2019, AtGames, a company specializing in replica microconsoles containing compilations of retro or retro-styled games, acquired a portion of the rights to Ms. Pac-Man from General Computer Corporation, the company that made the original Ms. Pac-Man game for Midway and Namco - this led to a lawsuit over the IP, with an undisclosed turnout. After this, Ms. Pac-Man would begin to disappear from Pac-Man games, implying that AtGames won the case, with Ms. Pac being replaced by a character named Pac-Mom, who has a visual design resembling Ms. Pac-Man's mother from Pac 'N Roll.

Pac-Mom first appeared in the Arcade Archives release of Pac-Land through graphical modification to the original ROM, and would then be named for the first time in Pac-Man Museum+ alongside modifications to other games that originally featured Ms. Pac-Man such as Pac-in-Time, and would appear again in Pac-Man World: Re-Pac in place of Ms. Pac-Man.

Ms. Pac-Man's final appearance in an original title would be on the Pac-Land stage in 2018's Super Smash Bros. Ultimate.

Despite sharing a name, two different announcer takes were used for Roy from Fire Emblem and Roy from Mario, with the announcer using a sinister tone for the villainous Mario Roy and a prideful tone for the heroic Fire Emblem Roy.

In Super Smash Bros. Ultimate, when Banjo either runs with the Talon Trot or uses his down special Grenade Egg, a flap on the bottom of Banjo’s backpack opens up to use said move. According to Steve Mayles (the original character designer for Banjo & Kazooie) on Twitter, this is a concept that he wanted to initially use in the original Banjo-Kazooie, but limitations of the Nintendo 64 prevented it.

The relationship between the protagonist of Greenhouse and Stanley from Donkey Kong 3 is ambiguous. The manual for Greenhouse - written before the release of Donkey Kong 3 - simply states the character to be named "The Fumigator", while print and TV commercials released after Donkey Kong 3 claim the character to be named Stanley, likely as a retcon of sorts to tie in with Donkey Kong 3.

Notably, Stanley is the only character from a Mario universe game that Mr. Game & Watch transforms into in Super Smash Bros. Ultimate, while moves based on games such as Mario's Bombs Away and Donkey Kong Junior have him retain his appearance as the pedestrian from Fire as he did in previous Super Smash Bros. games. Additionally, Super Smash Bros. Melee's trophy description for Stanley lists his debut as Donkey Kong 3 and not Greenhouse.

Contrary to popular belief, the Mushroom Kingdom stage in Super Smash Bros. does not use sprites or music from Super Mario Bros. - this can be noticed both in obvious ways, such as enemy sprites having complex shading that would be impossible in any NES game, let alone a title as early in the hardware's lifespan as Super Mario Bros., and multiple sprites being miscolored; and in more subtle ways, such as the ground blocks being one pixel too tall on the bottom and the outlines on the goal stair blocks being too thick. The background music, while an impressively close replica, uses subtly different instruments and is slightly slower in tempo.

In Super Smash Bros. Ultimate, the stage's graphics would be revised to more closely resemble Super Mario Bros., using graphics from Super Mario Maker, and the faux-8-bit Super Smash Bros. rendition of the overworld theme would be the sole battle song from 64 to be absent, in favor of the original NES rendition of the song.

In the launch version of Super Smash Bros. Ultimate, Marth and his clone characters were unable to dash-grab R.O.B. while he was in shield. This would eventually be fixed in Version 3.0.0, which increased the vertical range of these characters' dash-grabs.

Super Smash Bros. Ultimate's spirit list comes incredibly close to serving as a comprehensive list of all Nintendo IPs as of 2018, but is mostly lacking content from three specific categories:

• Games that did not receive Japanese releases, such as Tin Star, Magnetic Soccer, and StarTropics (it should be noted that characters introduced in localized versions of Japanese releases, such as Rusty Slugger from Rusty's Real Deal Baseball and the Elite Beat Agents, are featured).
• Arcade games that did not receive ports to Nintendo consoles, such as Monkey Magic, Arm Wrestling, and Sky Skipper. The only exception is Sheriff, likely due to his role as an Assist Trophy.
• Games released exclusively through the WiiWare service. Although there is a spirit from the Fluidity series (which originally released as a WiiWare title), the character in question depicted is Eddy, the main protagonist of the Nintendo 3DS sequel, Fluidity: Spin Cycle.

If you land while performing Luigi's forward aerial in such a way that his hand hits the ground, a special animation plays where Luigi shakes his hand with a pained expression on his face as if he hurt his hand and is trying to get the pain out of it. This animation can be interrupted by the player causing it, making it hard to notice.

Contrary to the official explanation about Kirby's lack of a Keyblade after inhaling Sora, there is an unused Keyblade model for Kirby, meaning that at some point in the development of the final DLC Fighter, Kirby would have indeed wielded Sora's Kingdom Key during the use of Sora's Neutral Special, but this idea was scrapped. The weapon can be found in the game's data but remains functionally unfinished, and even when the game is modded the Keyblade will not spawn in.

Tetsuya Nomura, one of the creators of Kingdom Hearts and the series' recurring director and lead writer, admitted in an interview with Game Informer that it was actually him, not Disney, that was almost hesitant for his character Sora to get in Smash.

"Obviously, I was very happy that we were able to have Sora make an appearance in Smash Bros. Ultimate. Most of the feedback when Sora was [announced] for Smash Bros. Ultimate was, ‘I can’t believe Disney okayed for him to be in this game.’ Behind the scenes, I was actually the one being very picky about his appearance in Smash Bros. Disney was the one that was like, ‘Go ahead! This is a great opportunity.’ I thought it would be tough to pull off because it might clash with the established lore in Kingdom Hearts and the Disney worlds, so it was an opportunity I had to consider very carefully. After seeing how happy everybody was in welcoming Sora to Smash Bros., I feel like the end result was really great."