When Sandy is de-anthropomorphized, the tail of her anthropomorphic form can still be seen poking out of her suit.
Sandy should not have gotten shocked by the jellyfish just by jumping on them, as the characters only get shocked by their tentacles, as seen throughout the series.
In a crowd shot of everyone looking at Neptune's moon, Squidward is among them. Later when it cuts back to the shot, Squidward had vanished (he'd gone to the bathroom). How he'd resisted the moon's hypnosis is unexplained, although it's likely that he felt that relieving himself was more important than looking at a weird moon.
One scene has a plane flying by filled with fish all transformed by Neptune's Moon. This isn't possible as, with the exception of the pilot, they were all sheltered from the moon.