Lisa's birthday is coming up, and she asks Bart to actually put some effort into her present this year. Meanwhile. Homer must wear a pink shirt to work after Bart puts his red cap in with the white laundry.
While at work Mr. Burns sees Homer with the pink shirt and believes him to be insane. Later he gets a sanity test from Dr. Monroe to bring home. Bart takes the test for Homer and he fails. Homer is promptly committed to a New Bedlam mental institution.
There Homer shares the room with a big white man who thinks he is Michael Jackson. Meanwhile, Lisa celebrates her eight birthday without a present from Bart. When Homer and Michael are released from the mental institution, Bart gets Michael's help and writes a special song for Lisa on her birthday. Lisa says it was the best birthday present she ever received. Michael suddenly talks in a normal voice, and reveals he is really Leon Kompowski, a bricklayer from New Jersey.