The international version's cover features the Tennessee Titans' former quarterback Vince Young, while the Spanish version has San Diego Chargers defensive end Luis Castillo instead.

At the start of the demo, you can see a poster in the subway for "Science Forum" with the question "Will Robots Surpass Humanity?" featuring Dr. Light and Dr. Wily. This is a reference to the two scientists from the Mega Man series.

Completing World 8 unlocks Sonic from the Sonic the Hedgehog series. This marks the first time a character from a different universe is playable in the Monkey Ball series.

Camelot president Hiroyuki Takahashi gave Luigi the main role in the story as a surprise to the player. Luigi had always been "stuck in his brother’s shadow ," and Takahashi wanted to give him a much larger role with as much prominence as Mario.

In the early stages of development, Pulseman was originally meant to play similarly to Magical Taluluto (based on the Shonen Jump manga of the same name), the first game directed by Ken Sugimori who was also the director for Pulseman.
For example, he originally had the ability to turn into a fighter jet and fly by pressing the jump button twice, but this was scrapped, as it didn’t fit his character.

The song "Senbonzakura" has been removed from every Korean version of the Project Diva games. The song makes many references to war and the revamping of the Japanese nation during the end of the 1800s, of which both Japan and Korea were feuding at that time. Even today, tensions still exist between both regions and the song was deemed too controversial for Korean audiences.

In a Q&A, the developers revealed that Shuma-Gorath was one of the first Marvel characters proposed, but Marvel was reluctant to allow them to use him, but Capcom eventually convinced them that he is popular and a big part of the series history, eventually leading to his inclusion as DLC.

According to Kyo’s designer, his final design was inspired by Jo Yabuki from Ashita no Joe, and Akira Fudo from Devilman.

Within the game's files are voice clips for five unused Create-a-Soul classes. These clips can only be heard in-game via mods or hacking. The unused classes are Noble, Scared Fighter, Beastmaster (Ranger), Clown, and Great Warrior.

Pulseman’s Japanese anime-inspired design was made as a direct opposition to Sonic the Hedgehog’s design, as Sonic was popular in the ‘90s and had a Western cartoon look to it. He was also made red to be opposite to Sonic's blue.

Orochi was originally planned as "a buck-naked Chris" fighting with a shining energy ball. However, it was changed after developers were surveyed and only two votes in favor of the design were received. His design codename was "Chief", however, a lot of people were against giving him the name "Orochi".

The Galarian Yamask has one of the most elaborate evolutionary methods in the entire series. In order to evolve it, the player must allow Yamask to lose 49 or more points of HP and then, with the damaged Yamask, the player must go under the large stone arch in the Dusty Bowl area. Immediately upon doing the latter, Yamask will evolve into it's Galar-exclusive Evolution, Runerigus.

Although not referenced in game, Pecker is a Monkaw (half monkey and half macaw).

The final boss of the game, the Patrickosaurus, is based on a character from a deleted scene in The SpongeBob Movie: Sponge out of Water, where SpongeBob and Plankton have gone too far back in time and encounter it along with the Squidosaurus (the latter of which was seen in the final film).

A line from the DK Rap from Donkey Kong 64 is referenced in Donkey Kong's bio by mentioning "He's so strong, it isn't funny".

SEGA partnered with Chiquita to promote the game by featuring it on banana stickers. There was also a sweepstakes in which the grand prize was a 50" Flat Screen, a large sofa, four gaming chairs, a copy of the game, a Wii balance board, Wii Fit Plus and various other Wii oriented prizes.

Monolith Soft, known for the Xeno series, had approached Nintendo in 2003 with a pitch for an Earthbound sequel, intended for the GameCube. The game was designed as if were made of arts and crafts, similar to Kirby's Epic Yarn and Yoshi's Woolly World, and was supposed to be set in America during the 80's.

The meeting for this new Earthbound game was arranged by Nintendo's then-CEO Satoru Iwata without Shigesato Itoi (Earthbound's creator) knowing about it. Despite Itoi not knowing about this project, it's unclear what led to the cancellation of the game.

A demo build of the game shows that Frogger would've had a lot more animations, including Frogger bouncing, doing a mid-air flip, and extra death animation, hopping to his left and right, doing a cartwheel, a "leapfrog" animation, panting, an alternate slipping animation with one slipping to the left and one to the right, a drowning animation, doing a super hop, two idle animations, kicking upwards while doing a handstand, and doing a "superstart."

The sinking and mid-air flip animations would later be used in the sequel.

According to writer Paul Gardner, there was originally going to be a character named Moronic the Plumber (a parody of Sonic and Mario) that took the role of a hero to reclaim stolen treasure from their dimension. Traveller's Tales rejected the idea, and Moronic was later replaced with a cameo from Spyro the Dragon.

The game was going to be remade by Eden Games, who developed the critically panned 2008 sequel to the series, also titled Alone in the Dark. After the mostly negative response to the sequel, the remake was cancelled.