During the recruiting scene, there is a string of square patio lanterns hanging behind the heroes (seen especially during the part with Buckethead). It disappears when they are interviewing the PMS Avenger, and when the Wonder Women are fighting.
At the beginning when the amputee's left prosthetic arm is taken off and thrown into the punchbowl, it changes to a right arm by the time it's hanging on the chandelier. Then it falls and reverts back into a right. It also starts off wearing a watch, but ends up wearing jewelry when attached to the chandelier.
After Lance Hunt reads Captain Amazing's "letter" during Casanova's trial, he folds it back up. However, in the next shot it is unfolded, then in the following shot when he puts the letter in his coat, it is folded up again.
In the diner, after The Shoveller, Blue Raja, and Mr. Furious are discussing recruiting, The Shoveller and Mr. Furious extend their pinkies and thumbs, but when shown from above, they are extending their pinkies and index fingers.
During the recruiting scene, the order in which the superheroes are standing in line changes from shot to shot. For example, after The Waffler auditions and walks away, he is seen still waiting in line behind Pencil Head & Ballerina Man. When the two Wonder Women begin fighting, he is no longer present.
When the Jitney crashes through Casa Casanova gates, several of the headlights are clearly damaged. Next time you see the Jitney in the grass plaza area heading for the mansion, the headlights are all intact and working. After the Jitney crashes through the wall into the main hall, some of the headlights are damaged again (as they should be).
Frankenstein tells Amazing that he'll be killed tomorrow at midnight. Later (presumably the next day), Frankenstein tells Tony P. that he will be having a banquet the following night for his gangs. However, several days pass before the Mystery Men attack the Casa Casanova.