Simpsons Season 7, Episode 25: Summer of 4 Ft. 2

At the start of summer, Ned Flanders asks Homer to take care of his beach house in Little Pwagmattasquarmsettport. The family decides to go there and Lisa, realizing that she is not as cool as she thinks, uses the new locale as a chance to rid herself of her nerd image and becomes a surfer girl.