Pattinson went pale in the face and went "eeewww."
The crowd loved the idea though and roared their approval.
Mind you, they pretty much roared from the minute RPatz walked through the door to the show.
The "Twilight" star was in town to promote "Remember Me," but the movie promotion got lost in the audience's full-on love for Pattinson.
Maybe it's the Brit accent?
A question in from Twitter provoked gales of laughter as someone under the name of "Sammy Tweet Tweet," asked if Pattinson would ever release an album, which set Fallon off on his riff.