T-Rex: The royal "we" is used by monarchs, popes, and also by dinosaurs named T-Rex. THAT IS ME, BY THE WAY.

T-Rex: Or should I say... that is US??

T-Rex: We think this is great, Dromiceiomimus! All our opinions sound much more important, now that they come from a grammatical PLURALITY. It's just classier to say "WE ate too much and had to go to bed early" than "I"! We did, by the way, Dromiceiomimus. We made some mistakes at dinnertime.
Dromiceiomimus: We understand, T-Rex.
T-Rex: Oh man, you're doing the "we" thing too? We mean, um, you babes are doing the "we" thing too?

Utahraptor: I think it just extends to pronouns: one of the several reasons you shouldn't call Dromiceiomimus "you babes"!
T-Rex: You guys think so?

Utahraptor: Yeah, and ALSO, we guys are worried you're going to end up sounding patronizing, like you're talking to a dog. "Aren't we just the cutest little puppy? Yes we are! Yes we are!"
T-Rex: We assure you we are not the cutest little puppy. We are the awesomest giant T-Rex; yes we are. Yes: we are.

Narrator: LATER: EVERYONE GETS TIRED OF T-REX'S "WE" AND DECIDES TO HANG OUT SOMEWHERE ELSE
T-Rex: A question for us! Do we miss having friends?
T-Rex: SOMETIMES we does, yes