Kirk describes his girlfriend Lulu as Manic Pixie Dream Girl - a woman who built him appreciate his life to its fullest. Castle describes her as a "deep-fried twinkie" - preferences excellent, but actually poor for you. This trope is referenced in relation to Nathaniel in "He's The New Guy", where she entreats her coworkers not to trust that their Bad Boss has a heart of gold just because some 'quirky girl' dated him for a whilst.