Revealing mistake: At the beginning of the movie, we see the three villains in front of several backgrounds. In most of these backgrounds, their outlines are fuzzy, indicating that they are actually standing in front of a green screen.
Visible crew/equipment: When the super baddies arrive on the moon and encounter the astronauts, the girl Kryptonian kicks one of the astronauts into space and you can see the strings around his waist as he floats away.
Other mistake: The phantom zone villains were captured and put in space near Krypton. When Kal-El was sent to Earth, he has to pass 6 galaxies to arrive (his father said, before Krypton exploded). When Superman sends the hydrogen bomb in Paris into space, he didn't even leave the solar system. No way the phantom zone travelled through 6 galaxies - it has no propulsion, and the shock wave from the bomb wouldn't travel that far either.Goekhan