The car was filthy when he returned it to me, and 'to cap it off' [='to top it off'], there was almost no fuel left in the tank.
a 'shower/bathing cap' [=a head covering that people wear to keep their hair dry when they are showering/swimming]
They may not like being called careless, but 'if the cap fits, wear it'. [=('US') 'if the shoe fits, wear it']
(..) Susie Moss! Right! Yeah! Wow! You look... Great job growing up. It's nice to see you don't still wear the cap with the mirrors on it. I graduated fourth grade and realized I wasn't a pimp. Remember the class play? You pulled up my skirt and the entire auditorium saw my underpants? (..)1996 TvShow: Friends Title: The One After the Superbowl: Part 1 Season: 2 Episode 12