Thirteen is a song by Big Star. It is considered by fans to be Eric and Donna's theme song. It is played three times in the series during scenes involving the couple. The first time is in "It's A Wonderful Life", when Eric is in bed remembering his break up with Donna. (though it was changed for syndication and home media releases) The second time is when Eric climbs into bed with Donna after returning from running away from their wedding. The third time is at the end of the final episode when Eric and Donna reunite for the first time after Eric returns from Africa. The song is also played when Donna is having flashbacks between her and Eric.