The My Friend, the Gorilla Affair - S3-E14
Continuity mistake: The giant (and obviously fake) spider is beside Marsha, crawling toward her extended right hand when Illya tells her to freeze. But when he clobbers the foam-rubber menace in the next shot, he attacks the grass behind her. And her right hand, stretched out on the grass when he said "Freeze," has instantaneously moved to her lap between takes. (00:29:05)