Ted Mosby:  Look , there 's a fine line between love and insanity . It 's the Dobler - Dahmer theory .
Lily Aldrin: Damn , I always forget the little _ one _ !
Ted Mosby: All right . If both people are into each other , a big romantic gesture works . Like Lloyd Dobler holding up the boom box outside Dianne Court 's window in Say Anything . But if one person is n't into the other , the same gesture comes off serial - killer crazy , or Dahmer .