Anthromorphic female 'ducks' are shown topless. So the breasts shown with nipples are more like human breasts covered in feathers but nipples showing. The context of the two scenes are both 'female nude' in nature. One is a photo in 'Playduck' magazine and the other is a female duck taking a bath.
Main character undresses down to her underwear to flirt with an anthropomorphic duck.
In a scene where Lea Thompson is on a bed with Howard, she moves around quickly and her breasts and nipples can be seen briefly. This is very quick and easily missed.