In the Japanese version of the game, there are files referencing planned train stations and dialogue involved in obtaining and stamping tickets. Each ticket would take you to one of 15 stations.

In an early prerelease version of Super Mario Sunshine, Delfino Plaza has a different look than in later prerelease versions and the final product.

Il Piantissimo is actually The Running Man from The Legend of Zelda: Ocarina of Time/The Postman from The Legend of Zelda: Majora's Mask.

In a 2002 developer interview archived by the now-defunct blog GSLA, director Yoshiaki Koizumi revealed that the game's staff originally came up with ten different nozzles for FLUDD, devising new ones for each possible situation Mario might encounter. However, this was reduced to three to avoid similarities to the gameplay style of The Legend of Zelda series. Some remnants of this larger quantity can be found in the final game's data, which includes an unused model for a Yoshi head nozzle and parameters for a sniper nozzle. While the former's properties are unknown beyond its appearance (with its model lacking any associated animations), the latter would have been 100 times more powerful than the Squirt Nozzle and would've had a significantly larger hitbox. However, it also would've required Mario to charge it like the Rocket Nozzle and Turbo Nozzle.

In a 2002 staff interview with Nintendo Dream, director Yoshiaki Koizumi revealed that FLUDD was inspired by his memories of playing with water guns as a kid, an image that he recalled upon first using the analog L & R triggers on the GameCube's controller. Series creator Shigeru Miyamoto further explained that the concept behind FLUDD was controversial among Nintendo's staff due to Mario not being widely associated with these kinds of tools, though Luigi's use of the Poltergust in Luigi's Mansion ultimately served as a precedent in the concept's favor.

In the same interview, Takashi Tezuka stated that Nintendo went to great lengths to keep FLUDD from resembling a firearm, both due to Koizumi finding a water gun "too simple" and due to concerns that guns (or anything that audiences may interpret as such) would be inappropriate for the franchise's public image. The "weird backpack thing" that FLUDD ultimately ended up as addressed both concerns at once, with Koizumi likening it to firefighting equipment and "a [plastic] bottle water rocket toy."