TV Show Friends – the United States, sitcom. (Season 3 Episode 23) ============== [Scene: Central Perk, Phoebe’s singing, Vince is also there.] Phoebe: (singing) “Crazy underwear, creepin’ up my butt. (Jason enters) Crazy underwear, always in a rut. ============== It is a silly song, I know, But: Is it correct to say "creeping up my butt" instead of "creeping my up into my butt"? and what does "in a rut" add to the previous sentence? Is she saying that the underwear is like a lion that wants to eat her butt?