jerimiah

Revealing mistake: In the scene where Kevin goes to climb the shelves, we can see that the tarantula is fake as it doesn't move, nor would its legs be spread out if it was holding onto the side of the glass tank as shown.

jerimiah

Revealing mistake: When Marv is at the basement door trying to regain his stance, as he steps onto the icy ground, the "ice" bends and distorts the light just like a piece of plexiglass.

jerimiah

Revealing mistake: When Harry and Marv are crossing the "rope" to the treehouse in the far away shots it is something thinner and resembling more like a steel cable, not a rope as Kevin had put up.

jerimiah

Revealing mistake: When Harry trips on the fan string throwing feathers all over him, the fan sound is heard running but there's no air blowing at him as the feathers are falling around him undisturbed. A few shots later, we see the fan on and blowing feathers around the room which is what it should have been doing.

jerimiah

Revealing mistake: When Kevin lands in the treehouse, he's at the back with his feet through the wall. Given where the rope is tied to the tree, he would have hit into the tree or the door frame of the treehouse, not at the back wall.

jerimiah