F lying in bed, getting ready to go to sleep, with his back on the bed and his legs up against the wall.

B: Lie down, monkey. It's time to go to sleep.
F: But I'm being an [something that sounds like "elf"]
B:: You're being an ELF?
F: No! I'm being an [same word that sounds like "elf"]
B: You're being an L?
F: Yeah! I'm being an L!