Rayman Raving Rabbids 2 (Nintendo DS)
November 13, 2007
The Nintendo DS version of Rayman Raving Rabbids 2 features a minigame called "Lunch Time" that takes place in a construnction site and consists in tapping the touch screen to make the player's Rabbid walk on a girder to reach a packed lunch at the end before the two rival Rabbids. The player must stop tapping to make the Rabbid cower and avoid swinging objects that would knock him down.
One of the swinging object is a green pipe likely shaped after a Warp Pipe from the Mario series.
Additionally a preview image of the game featured a Rabbid dressed like Mario, possibly indicating that there was originally intended to be one, but was later scrapped.
Rayman Legends (Wii U and Nintendo Switch)
August 29, 2013
The Wii U and Nintendo Switch version of Rayman Legends features exclusive costumes for Rayman and Globox based respectively on Mario and Luigi.
Since in promotional material these costumes are specifically called "Mario & Luigi", it's possible that they were intended to be based specifically on the Mario & Luigi series.
The creators of Rayman Raving Rabbids, had no right to use elements from the Mario series, so they only included a subtle reference in a minigame. Also the Mario-Rabbid was possibly removed from the game to avoid issues with Nintendo.
When creating Rayman Legends, however, they got the license from Nintendo to include the Mario costumes, as a form of double way marketing.