OK, I'm going to mix it up a bit! My dominant Aboleth does this sometimes, because she knows she can mug it off Lopsy or hump his face until she gets her way. It only happens when we turn up with food and she's busy in the loo: she finishes up and comes bowling over. Obviously she doesn't need the nudge though.
Lopsy sometimes just doesn't notice as well: if he's in the house and the food's outside, we have to get his attention or Aboleth'll eat it all. He's mostly deaf and there's a lot of angles he can't see (hangy ears) so it's totally 'normal' if we've caught him at the wrong angle.
I suspect Mouse might have had stick off Boo, to be honest, and she's been playing it over-cool so Boo doesn't have to reprimand her again, poor Mouse!