He remembers Kevin attended special needs classes in elementary school. Now, with Dee on a mission to prove her brother wrong, Mac has a pitch for the gang.
They need to start their own band, because if a retard can do it and get laid, they certainly should be able to!
Mac then invites Frank to take he and Charlie out to buy instruments.
After choosing a guitar based entirely on how he looks when he holds it, Mac is shocked to discover that Charlie can actually play keyboards.
Mac, Charlie and Frank decide to start their own band but can't agree on what genre of music to play, and Charlie pens a disturbing song about a strange creature called "The Night Man".
"Sweet Dee's Dating a Retarded Person" is the ninth episode of the third season of It's Always Sunny in Philadelphia.
When she discovers that Kevin still lives with his mother, it doesn't help his case for "normal." Dennis inflates his score very quickly which frustrates Dee to no end.