"Mmmm. An entire cheese pizza all for myself!"

I think Kevin says that line simply because of the events of the first act that result in him being sent to the attic. Little Fuller and Buzz likely shared the only pizza that had just cheese on it. There is nothing wrong with that, but Kevin likely got revenge by ordering a cheese pizza for himself, and with Buzz's money. Hopefully Peter punished Buzz severely because it was his actions before they left that caused Kevin to be left home.

"Mmmm. An entire cheese pizza all for myself!"

I think Kevin says that line simply because of the events of the first act that result in him being sent to the attic. Little Fuller and Buzz likely shared the only pizza that had just cheese on it.