Factual error: A guy dancing at Arnold's is wearing red Nike sneakers with a white swoosh. Nike was founded as Blue Ribbon Sports in 1964, and the Nike name and swoosh were not created until 1971.
Visible crew/equipment: When Don comes into the garage to apply for the job, the T-mark can be seen on the floor by Fonzie's feet.
Revealing mistake: When Arnold's burns down you can see the set walls wobble a lot.
Ralph's Family Problem - S7-E25
Factual error: Fonzie takes Ralph on a motorcycle ride to make Ralph feel better, but they are roaming through hilly areas. There are no hills in or near Milwaukee.
Answer: If all the actors and hands know their roles well enough they could perform the play reasonably well even without a director.
BaconIsMyBFF