At Lily's soccer game, Joe says, "Mommy shot Jay, Aunt Claire said, 'shoot him'." Since Jay is both Claire's and Joe's dad, Claire is Joe's sister, not his aunt.
Gloria's pellet gun is clearly pointing nowhere near the sippy cup when she pulls the trigger and the sound effect is played, yet the sippy cup goes flying nevertheless, indicating the motion was actually triggered by something other than the gun.
Cameron seems to be allergic to dogs and asks Mitchell if he forgot to mark 'no dogs' on the latest rental agreement but last season Cam was eager to take in and keep Stella when Gloria thought Joe was allergic to dogs.