U.S. Postal Service regulations prohibit uniformed employees from drinking in public, yet Cliff does so throughout the run of the show.
Norm and Paul ruin half the bar moving the piano including an entire wood wall with spindles but it's all completely fixed by that afternoon.
When Rebecca enters Russell's room, the last shot shows the edge of the floor's carpeting revealing it's a set.
During the scene when Cliff is conned into wearing the gag uniform, Norm's beer serving goes from a snifter, to a mug, and back to a snifter.