Angry Video Game Nerd: The Movie (2014)

Revealing mistake: About seven minutes in, during the scene where we see Cooper helping the Nerd as a cameraman, you can tell that Cooper has been added to the scene using green-screen effects, as the actor was unavailable to shoot at the location. The lighting on Cooper doesn't quite match the lighting of the scene, and you can see a slight "blur/feathering effect" around him where the greenscreen background was removed.

Trivia: Directors Kevin Finn and James Rolfe grew up watching cheesy B-movies, and decided to model this film after the low-budget nature of such productions. Hence, they included frequent convoluted plot-twists and purposely-bad special effects. (Such as low-quality miniature models.) However, while most audiences understood that the low-quality of the effects were part of the "joke" of the film, some audiences failed to realize this, and the film received some initial backlash online from people complaining about the effects, not realizing it was intended to look cheap and silly.