Other mistake: Pay attention to one of the early innings of the baseball game as one of the Angels players hits a home run. Though probaby intentionally set up this way as to avoid any problems of "logo patents" and such with the real life MLB California Angels team, he is wearing a helmet without the team logo on it. (01:07:35)
Other mistake: While Frank Drebbin is saying the words "dew glistening on the grass" you can clearly see a woman in the audience at the bottom of the screen repeating every word he says. (01:19:55)