After the Ghostbusters get their proton packs back, when the possessed Megazoid says "Noise, too much noise, be quiet", it's teeth disappear for a couple of frames.
The movie poster that Slimer crashes into is misspelled "Ghostbuters" when seen in the wide shot. It was correctly spelled in the preceding close up.
The Ghostbusters leave New York at night, but arrive in Burbank in the morning after a flight that should take only three to four hours. Because California is three time zones east of New York, they should have arrived at night.