You see the Mario costumes in Super Smash Bros for the N64, Mario Party 4,5,6, and 7, Mario Superstar Baseball and Super Mario Strikers for the GameCube.
Yes YES! It's been too long since there's been an alternative to the Madden games. Imagine Waluigi and Luigi as wide receivers! Super Mario Touchdown - let's do this Nintendo!
Retro Studios almost made a Mario Football, but they changed it to a cancelled NFL game due to Nintendo wanting the studio to work on a realistic sports game before focusing on Metroid Prime.