Contrariwise, the peeps don't really seem to take much notice of the pets anyway. If you (usually accidentally in my experience) drop a peep on a pet they'll 'pet' it, but otherwise they ignore them. Perhaps there could be a one-off boost to the peeps' happiness when a pet is added to the house, and also a self-starting action added for the peeps to 'pet' or 'play with' a pet occasionally. Ideally, that would give a small rise in the peep's happiness as well.