The creator of Waluigi said that the "evil Princess Waluigi" he designed was not used in 2004's "Mario Tennis"

Recently, it was revealed that Nintendo's Mario series has new characters that have not yet appeared, and the designer Fumihide Aoki who officially designed the "Waluigi" character provided this information. Aoki Fumihide shared several design pictures of his look on his personal Instagram account, including some sketches and renderings. And the character he designed is the evil version of Princess Peach - "Princess Wabiki".

From Fumihide Aoki's description, we can know that this short, innocent-looking Princess Waliki in a purple dress is just like the evil version of Luigi "Waluigi" he designed for "Mario Tennis 64" (July 2000), which had insufficient optional humanoid characters. Due to the lack of optional characters in "Mario Tennis GC" (October 2004), this reverse version of Princess Wabiqi was designed.

However, perhaps considering that "there are no matching characters", or the existence of the evil version of Princess Peach itself is "unacceptable", Nintendo ultimately did not adopt this reverse character who would treat Wario and Waluigi very horribly when angry.