Early in the movie, when the Peter Brown character wanders into a Kosher restaurant, the menu shown lists Salami and Cheese at the very bottom, which is definitely not Kosher, as meat and milk items may not be combined into one dish. Then he proceeds to order bacon, which would definitely never be served in a Kosher restaurant.
At about 0:06:20 the boom mic shadow appears in the wall above Joe E. Brown as he stands next to a table.