Thought you might ask :)
From RMDupree:
I get a call at work from my mom who had just come back from the school. The kids had started the last song (O Christmas Tree) when all of the sudden, the kid standing directly behind Rebecca got sick.
She vomited on the back of Becky's pants.
Becky's retelling was funny though. She sings the last line and halfway through "branches" she makes the nastiest vomit sounds. Eeeewwww!
So "singing 'branches'" means to bazooka-barf on somebody :)
I'm feeling funny. pizza!
What he means is he is feeling silly and full of laughter, and is excited about eating pizza for supper.