Goofs

During the "poo on the wall" scene, the splatter on the wall moves after Grandpa makes it. Also the woman sitting behind Billy isn't there but then appears when Grandpa and Billy get up to leave.

In the diner where Irving and Billy are having their farting contest, Billy is seen eating his breakfast, when shown again he is eating chicken parmesan.

In the restaurant, just before Irving farts for the first time there is an old women sitting on table to his left, and a man with blurred face is sitting behind Billy. In the very next scene the same woman is sitting on the table behind Billy and the man with blurred face is gone.

When Billy is sitting with Lisa and doing the thumb war she's wearing her coat. When Irving comes along, her coat is off.

When Billy and Irving first get the motel room, the door is on the left with beds to the right. The next morning, when Billy trips over grandma's body, the door is on the right and beds to the left.

During and after Irving goes through the store windows, the mattresses and the chairs look like they are already set up.

When the guy comes out of the restaurant to complain and argue with Irving about the penguin, he smiles and laughs several times.

Irving and Billy need the help of two movers to move Ellie's body into Irving's trunk from his house, but they are able to bring the body into a hotel room by themselves with ease.

Billy and his Grandpa were supposedly meeting his biological father in Raleigh. After meeting the father and leaving the biker bar, the city skyline shone is actually that of Charlotte, not Raleigh.