Plot hole: The Kaiju's EMP pulse fries all electrical circuits next to him, and affects the base as well. If that's true, how did the helicopters carrying Gypsy survive the blast without having their electronics fried? EMP pulses induce current in all electronics regardless of whether they're powered on or not.
Factual error: Gipsy Danger's fist bumps into an office table as it screeches to a halt. The Newton's cradle on the table has an impossible reaction. All of the balls would simply sway in parallel, and not the 'classic' reaction displayed in the movie.
Factual error: The coastal wall in Sydney is shown as being inside the Sydney Harbour (right next to the Opera House). But Sydney Harbour is not on the Pacific coast but a part of the Parramatta river, several kilometres from the ocean (where the wall should have been). So the wall is either not shielding the northern part of Australia or (more likely) the producers decided that the audience cannot tell that it is Sydney unless we see the Opera House.
If you listen to track 1 of the soundtrack, Gipsy Danger's signature horn can be heard at various points.
Crimson Typhoon was originally planned to have four arms and be piloted by female quadruplets. However, the producers couldn't find any.
Stacker Pentecost: Today at the edge of our hope, at the end of our time. We have chosen to believe in each other. Today we face the monsters that are at our door, today we are cancelling the apocalypse!