His Swollen Dunussy

Okay, look here. This picture shows a person dressed up as a Dunkin' donut. The joke, you big dummy, is that 'dunussy' is a blend of 'Dunkin'' and a bad word for a certain part of the body. The meme suggests that the donut costume looks like it's swollen in a way that relates to this vulgar term. You probably thought it was hilarious, didn't you?