Super Chick Sisters

PETA made this Flash game featuring Mario and Luigi expies Nugget and Chickette, respectively, on a quest to rescue PETA spokeswoman Pamela Anderson.

Not to say that Mario and Luigi don't show up in these games, because they do, usually as the Butt Monkeys. There's also the blatant trademark infringement on Nintendo characters, though that might also qualify for a fair use exemption as parody.

The first game can be found here and its sequel, New Super Chick Sisters, can be found here.