A woman is shown naked later in the film with a man.
Brian encounters a nude man sitting in a hole. He has a beard that is long enough to cover full frontal nudity, although we get shots of his behind showing his testicles for a few frames and also his buttocks. This character is not meant to be arousing and is played for laughs.
The main character wakes up nude after sleeping with a woman the previous night. You see his butt as he walks over to open a window, he opens the window to a crowd full of people where full frontal male nudity is seen for a brief second.
There is one scene where a man and woman wake up nude. Then the women is seen nude as she gets out of bed, pubic hair, buttocks, and breasts are shown. The man walks over to the window and his buttocks are shown. Then the man opens the window and we get a full frontal shot with his penis on full display.