Dug: My master made me this collar. He is a good and smart master and he made me this collar so that I can talk. Squirrel!.My master is good and smart.
Carl: It's not possible!
Dug: It is, because my master is smart.
When the house first becomes detaches from its foundation and becomes airborne, Russell is nowhere to be seen, although every angle of the house is shown, including underneath, the front porch and the back porch. He knocks on the door and tells Carl he chased a "snipe" under the porch - but he cannot be seen after liftoff and prior to knocking.
When Carl's house begins to lift and the little girl looks out her window, the Luxo ball from Pixar's other films is seen in her room.