Franchise: Sonic The Hedgehog

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 Ōshima wanting to give the characters designs that were easy enough for kids to draw.

The English script for Sonic Colors, as well as other 3D Sonic localizations up to Sonic Forces, was partially written by Ken Pontac, known for working on children's programming such as LazyTown, Arthur, and Bump in the Night (the latter of which he co-created), and Warran Gaff, best known for his and Pontac's work together on the adult cartoon Happy Tree Friends. Pontac and Graff's renditions of Sonic were significantly more lighthearted than earlier or later 3D games, a highly requested shift at the time that would prove controversial after a few games. This disdain for Pontac and Graff's writing style led Pontac to decline from doing Sonic panels at conventions out of fears that vitriolic Sonic fans will visit and harass him.

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 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.

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.

Jon St. John, the voice of Duke in the Duke Nukem games, also voiced Big the Cat for several Sonic games starting with Sonic Adventure up until Sonic Heroes.

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 & 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.

During the reboot of Archie's Sonic the Hedgehog comics, several characters and aspects adapted into the comic from the 1993 Sonic the Hedgehog cartoon (commonly referred to as "Sonic SatAM") were noticeably altered for a variety of factors:

• Ixis Naugus (referred to simply as Naugus in the show) was changed to "Walter Naugus". His species (which was never actually stated in the show, though the pre-reboot comics depicted him as a rhino-bat-lobster hybrid) was changed to that of a troll, with a tail being added to his design to help make him look as such, alongside his attire being updated to more resemble a warlock. Additionally, despite what was initially believed, the term "Ixis" was originally applied to Naugus' cartoon production materials, and was not invented by former writer Ken Penders. This meant it was still usable in the comics, and was later given to the deity worshipped by the troll species.
• Muttski was changed to "Ben "Mutt" Muttski", and was changed from a non-anthropomorphic dog to an anthropomorphic one. Notably, his new name was given in honor of Ben Hurst, the main writer of "Sonic SatAM" who sadly passed away in 2010.
• Snively Robotnik (referred to simply as Snively in the show) was changed to "Doctor Julian Snively", with his first name being a nod to "Sonic SatAM", as Dr. Robotnik's original name in the show was Julian. According to Ian Flynn, he is no longer related to Dr. Eggman in the reboot due to Sega's mandates not allowing other media to invent family members for the main "SegaSonic" cast. Ironically, while his half-sister Hope Kintobor was removed from the reboot, Snively inherited her position as G.U.N.'s R&D Specialist.
• Maximillian Acorn (referred to simply as "The King" in the show) was changed to "King Nigel Acorn". His name was most likely changed due to being coined by former writer Ken Penders. Notably, his new name, speech pattern and mannerisms are shared with Nigel Thornberry from the animated series "The Wild Thornberrys": Nigel was voiced by British actor Tim Curry, who also voiced the King in "Sonic SatAM".
• Nicole the Holo-Lynx's new backstory in the reboot has her being created by Dr. Ellidy in an attempt to digitize the consciousness of his dying daughter Nikki. This may have been loosely inspired by Ben Hurst's plans for the cancelled third season of "Sonic SatAM", where it would have been revealed that Nicole was originally a normal girl until she was tricked by Dr. Robotnik into having her entire personality transferred into a computer satellite.
• Although the Wolf Pack originated from "Sonic SatAM", the only member of the group who was not created by Ken Penders was their leader Lupe the Wolf, who also originated from the show. As such, when the comic was rebooted, she was the only member of the group to be carried over.
• Aside from King Acorn, the only parent of a "Sonic SatAM" character to make it into the reboot was Sabina, the mother of Dulcy the Dragon and herself a character from the show. However, while Ian Flynn did confirm that she was still Dulcy's mother in the reboot, she never actually appeared in the comic prior to its cancellation. Additionally, given that Dulcy refers to her with present tense, it's likely that Sabina is still alive in the reboot, whereas she had died in the original continuity.

In 2022, Logan McPherson, the director of the animated series "Sonic Prime", stated that the show was canon to the games, drawing upon their existing mythology. This would make Sonic Prime the first television series based on the Sonic franchise to be considered canon to the mainline series. Ian Flynn would further support this claim, revealing that he knew when exactly in the series timeline the show took place in, but would not reveal it until after the show ends, while noting that something happens in the show to make it clear that it is indeed canon to the games. In 2024, after the release of Sonic Prime's third and final season, Ian Flynn finally confirmed the show's status in the overall Sonic timeline: aside from taking place sometime after the events of Sonic Advance 3, the show's placement is considered moot due to the ending Spoiler:having the show wipe itself out. In response to complaints regarding this outcome, Flynn claimed that its placement in the canon was intentionally vague, and the show being canon to the games at all was not his decision due to only being involved in the animated series as a consultant. He later claimed that he and other parties had made efforts to flag the show's inconsistencies early on in production, but that many of these efforts were flat out ignored. He noted that there was not an easy way to brush these issues aside, but also made a point that there was an effort to do so.

In the 41st issue of the IDW Sonic the Hedgehog comic book, Sonic taunts Dr. Eggman with the nickname "Baldy McNosehair," to which Eggman responds with "That's not funny! It's never been funny! It's never going to be funny!" This is a reference to the YouTube channel TeamFourStar and their web-series "Dragon Ball Z Abridged". Specifically, it references the video "DragonBall Z KAI Abridged Parody: Episode 2" in which Krillin dubs himself, Gohan, and Vegeta as "Team Three Star", and Vegeta yells the same response.