Mary-Therese Tribbiani is one of Joey's sisters.
She has feelings for Chandler after Joey's birthday party and kisses him at a dinner at her parents' house. Chandler thinks she is Mary-Angela, and rejects her. Mary-Angela enters almost immediately after he asks Mary-Therese which one Mary-Angela is.
In Joey, Mary-Therese has been renamed Mary-Theresa and has virtually no similarities to the Mary-Therese in Friends. She is Joey's second youngest sister and extremely spoiled. She is seen in only one episode, Joey and the Fancy Sister.