Godzilla vs. Gigan uses a lot of stock footage from other Godzilla movies and, thanks to careless editing, other monsters make unexpected cameos. Right after the scene where the human characters rescue their friends from the Godzilla Tower, there's a stock footage shot of Godzilla running toward King Ghidora (the three-headed monster). If you look by Godzilla's legs you can see Mothra, the caterpillar. In another shot a few minutes later, taken from a different Godzilla film, Godzilla is seen on the ground and then stands up very quickly. If you look on the ground you can see the wing of Rodan, the flying monster. The fact that these obvious mistakes made it into the movie is living proof of how little time and money was spend on Godzilla movies in the 1970's.