This is solidified by the moment a second before the move, however, as he taps the Gorilla on the shoulder, and says, "I don't like getting hit in the ribs."
After a short and insane series of events, in the same storyline... the dialogue sums it up.
“Dude,” Calvin’s first head said to his second, “Did you just eat Godzilla?”
“Yes. *gulp” His second replied, “Yes I did.”
“That is quite possibly the coolest thing we have ever done or ever will do.” First Calvin said.
