Transcript:
Red: Rover, let's play "Star Trek" I'll be Kirk, you be Spock.
Rover: I was Spock last time. I wanna be a Tribble!
Red: You're too big to be Tribble, silly.
RoveR: That's the whole point. It takes a lot of food to grow into a Tribble my size.
If this were set later, he could be Commander Woof.