Revealing mistake: Very obvious ramp hidden behind the stall to allow for the cop car to jump.
Revealing mistake: When the microlight is flying, Tim Robbins' stunt is very noticeable.
Continuity mistake: When Lt. Welker meets Howard his arm is bent. A shot later it's raised.
Visible crew/equipment: When Dr Jenning is driving his stunt is very noticeable.
Revealing mistake: When they're riding with Jones look closely in some shots and you'll see Lea Thompson's stunt double.
Continuity mistake: For a few moments during the flight scene near the end of the film Tim Robbins has no handcuffs on, but they are back on again seconds later.
Deliberate mistake: When Howard is being sucked out of his planet by the laser beam the couch ignites but he doesn't.
Answer: As she said to Howard, she believed that he was using his "outlandish" appearance to be unable to find work and collect money through unemployment. She's probably dealt with people who did the same thing and was eventually sick of it.