The "Joyota", a supposed Jeep with a Toyota engine, is actually a Volkswagen 181 (known in the United States as the Volkswagen Thing).
During the opening sequence where they are snowboarding and playing paintball, they are shooting a number of paintballs. There is no hopper on the paintball guns, yet they seem to fire many shots.
Grandpa and Grandma G's residence is supposedly in Yakima, Washington. But in the shot where the guys check out Grandpa G's car for the first time, the skyscrapers in the distance are too numerous and too tall to be the skyline of Yakima, a small central Washington city.
The drummer in the band is wearing a different shirt in one shot.