Mary Elizabeth Ellis (born May 11, 1979) is an American actress. She is best known for her recurring roles as The Waitress on the FX comedy It's Always Sunny in Philadelphia (2005–present), Nick's ex-girlfriend Caroline in the Fox sitcom New Girl (2011–2018), and Lisa Palmer on the Netflix horror-comedy Santa Clarita Diet (2017–2019). She starred as Amy in the shortlived NBC sitcom Perfect Couples (2010–2011) and Debbie Sanderson in the Fox sitcom The Grinder (2015–2016). Wikipedia