Hot Tub High School is a low-budget movie released in 2000. A young Chloe Decker appeared naked in the film.
In "Pilot", Lucifer remembers seeing Chloe in the movie.
In "Everything's Coming Up Lucifer", Lucifer mentions the movie title to Chloe.
In a flashback in "My Little Monkey", John Decker, Chloe's father, gives tickets to the film to Petey, a Korean shop owner. He refers to Chloe as "My Little Monkey" and says he's proud of her. Petey mentions the "funny business" about 15 minutes in and John asks Petey to tell Chloe that the movie was good.
In "They're Back, Aren't They?", a suspect believes that Chloe and Lucifer coming to arrest him is a prank played by his friend, the victim of the episode. When confronted by them, the suspect states that part of the reason was because he recognized Chloe as "the chick from Hot Tub Hotel." Lucifer tells the suspect it was actually Hot Tub High School and that "she wasn't in the sequel."