When Babs says, "You're all in!", Montana Max and Dizzy Devil can be seen in the group of characters running across the screen. They were supposed to be formally introduced in a later scene where they emerged from a box of villains.
When Buster creates Acme Acres, its name is already on the drawing before they decide what to call it.
When Babs reads the "Audition Today" sign, her lips don't move.