Within the data of Kirby's Return to Dream Land is an unused plains theme, labeled KbyW_HEITI1 in the game's code. The song features a leitmotif in its second portion which is also quoted in "Beyond the Hill" and "Perfect Sledding Weather", with a variation also appearing in "Onion Ocean". Curiously, this leitmotif is also featured in the final boss theme in Kirby's Epic Yarn. Given that the leitmotif has no apparent narrative significance, it's possible that KbyW_HEITI1 originated from one of the three cancelled Kirby games for the Nintendo GameCube that eventually evolved into Kirby's Return to Dream Land.

The original Japanese commercial for Kirby's Adventure depicted the game's characters made of yarn. This is thought to have inspired the art style of Kirby's Epic Yarn.

The game was originally going to be a different IP called "Fluff's Epic Yarn". According to Etsunobu Ebisu, the original idea came from Madoka Yamauchi. The idea was presented to Nintendo after the developers at Good-Feel were done finishing the design document for the game. Nintendo asked the developers if they'd make it into a Kirby game, as Prince Fluff's design was similar to Kirby's.

The Design for King Dedede's Castle from the "Kirby: Right Back at Ya!" anime is reused in Kirby: Squeak Squad, Kirby's Epic Yarn & Kirby: Mass Attack, with Squeak Squad featuring the Monster Machine from the anime in the throne room.

In the Japanese version, King Dedede's narration often has him ending his sentences with the word "-Zoi" which really doesn't mean anything. This is a refrence to the Kirby Anime where in the Japan version, King Dedede also had this verbal take.

The narrator in the European released has a British accent, and instead of stating that the grass in the introduction "feels like pants" will state that the grass "feels like trousers". This was changed to accommodate the difference in the use of the word pants. Several other lines throughout the game have minor differences, too.

When Kirby and Prince Fluff perform the Kirby Dance after completing the level, Kirby will sometimes transform into an umbrella. However, this transformation is never seen nor used anywhere else in the game.