Jerry's signature on the photo shown at 13 mins is noticeably different from the one at 50 mins.
When Elaine lies in the magic circle, the sleeves of her robe are at her elbows, then at her shoulders, then at her wrists.
Elaine is shown driving south along the coast when she's stopped by the police officer, but it's later established that she came from San Francisco, which is reinforced by her subsequent course north through Eureka on her way to Arcata.
When the police pulled Elaine over in her car, he said her tail light was broken. Even though it was daytime, if the light fixture were broken, it could still be seen in the daylight.
Elaine performs a seductive dance for Richard, causing him to bite her rear end in a fit of lust. Before he bites her, red bite marks are already visible on her right buttock from previous takes.