Grandma Jack - S8-E7
Visible crew/equipment: Notice the scene when Terry comes out of the kitchen. As the kitchen door begins swinging shut, a mysterious hand (which belongs to a crew member) suddenly appears from offstage to keep the door closed. (00:07:10)
Grandma Jack - S8-E7
Other mistake: Larry entered Jack as "Grandma Tripper" to win the contest since the contest was only open to women. However, since Larry admits he didn't know there would be a bake-off and thought a winning check would just be mailed, then there's no reason to of entered Jack as "Grandma." He easily could have just entered Janet or Terri using Jack's recipe.
Grandma Jack - S8-E7
Character mistake: Jack says to Larry (upon finding out "Grandma" Tripper won the contest), "You want me to dress as a woman?" as if he never did that before and thought the whole idea was crazy - but earlier in the series he dressed as Chrissy in full drag so he's not new to the idea like he made it sound. Larry also dressed as a woman in an earlier episode as well (just for the record).
Answer: Richard Kline and Don Knotts were supporting cast members, who could be replaced at anytime. It was John Ritter, Joyce DeWitt and Suzanne Somers who were the star vehicles they relied on to carry the show.