TedStixon

Revealing mistake: During the car chase, when Mario and Luigi have the cops on either side shooting the guns, Mario screams "Brace yourself, now!" When he says this, you can quickly see Mario and Luigi have been replaced by stunt drivers. Also, Mario's mouth isn't moving. It happens quickly, so slow motion helps, but isn't required.

TedStixon

Revealing mistake: When Mario and Luigi's police car drives off the civilian's car they're stuck to the top, you can blatantly see a metal special effects line that's pulling their car down.

TedStixon

Revealing mistake: When the old lady falls into the car, she blatantly turns into a dummy for a few shots. (She literally doesn't move at all and is unnaturally stiff.)

TedStixon

Revealing mistake: When Mario and Luigi first arrive in "Dinohattan" and fall through the railing, you briefly get a clear look at Luigi's stunt-double, who appears to be a bulkier man who looks nothing like John Leguizamo. It goes by quick, so it can be hard to see, but once you notice, it's obvious.

TedStixon

Revealing mistake: When Daisy takes Luigi to the dig site, there's a long wide shot as they talk and start to head down. As the camera zooms in, you can see the composited background (the bridge, city, etc.) "jiggle" slightly towards the end of the shot where the composite effect didn't quite align up.

TedStixon

Revealing mistake: In the opening, when Daisy's mother pushes the beam and causes the cave-in in the mine, for a split second, you get a pretty clear shot of Koopa's stunt double, who is taller than and looks nothing like Dennis Hopper. He's only on-screen for about a half-second, but it's very easy to notice it.

TedStixon

Revealing mistake: When the meteorite strikes the Earth at the beginning of the film, there's an odd slip-up in the effect. About a half-second before it hits, you can sort of see it awkwardly shift slightly to the right for a split second. It's hard to catch, but once you see it, it's fairly noticeable.

TedStixon