As she prepares for the big dance, Elena is shocked to discover she has a “mustache.” Attempts to fix it only make it worse, forcing her to “own” her look. Bobby and his buddies plan a prank for the dance, but when it doesn’t go the way Bobby expected, he lashes out at Liam. Gabi’s discomfort with her new relationship only grows when her mother invites the entire family over to meet Sam.