Art director Tadanori Tsukawaki designed Wario to be a strongly masculine character: "I thought Wario was pretty manly. He's so uncool that he ends up being extremely cool. Depending on the game, he can be coarse - farting and doing stuff like that - but I didn't want to show that side of him. As much as possible, I wanted to show a macho Wario, one who is masculine and tough."
The creators considered developing the game using 3D graphics, but decided upon an anime style which would best express Wario's fluid, dynamic movements.
Queen Merelda was named after the green jewel emerald (her name is an anagram of "emerald"). Thus, she is seen in a green dress throughout the game.
Producers Takahiro Harada and Etsunobu Ebisu envisioned this to be "the ultimate 2D game" by having everything hand-drawn, from the characters to the backgrounds. According to art director Tadanori Tsukawaki, this was a titanic task of production: a single action taken by one character amounted to about 30 animation frames, resulting in 6000 enemy patterns, with 2000 more for Wario alone in order to animate the roughly 200 actions he can perform. The backgrounds were non-repeating and hand-drawn, and just as any change to a character's design required all the frames to be adjusted, even a small change to the background meant everything had to be changed. In the end, however, he felt it was worth it and sees this game as one of his best ever.
The Shake King was deliberately designed to have similarities to Wario (bulky build, wonky moustache) to make him a villainous parallel.