Continuity mistake: When they get to the beach to surf the windows in the truck are left open, but after the shark attack Byron comes running back to call 911. The windows are now closed, so he has to throw the rock at the window and get the cell phone.
Continuity mistake: None of the games in Goon were played in Manitoba, but every rink has Manitoba Liquor Commission advertising on the boards. In the game played in Quebec the advertising on the boards disappears in the zoomed out camera shots and you can see the MTS Centre logo on the scoreboard.