Isn't it right to say "didn't you" not "did we" considering the meaning? I'm curious why he used positive which is "did" and "we" (but it seems like asking to Ron alone).
It is actually acceptable to use "we" sometimes in place of you to address a second party. And so here "we" is in reference to a singular person, Ron who is alone. In British English sometimes we use the positive as a sarcastic query for what is an obvious answer. Here obviously Ron had a late-night snack, so the use of the positive "did we" is sarcasm. Ex: How are we feeling today? Ex: What are we in the mood for?