In the massage scene, Fred is lying face down on the table, but his feet are pointing upwards.
The "runaway bathtub" conveniently stops at a red light, giving Fred the opportunity to fall into it, then starts rolling again when the light turns green, with no push to get it started.
When Barney is pushing the bathtub on wheels to the singing audition, he tells Fred he is worried that his landlord will find out the tub is missing, but Barney owns his home.
During the gravel pit rehearsal of "Stoney (Swanee) River", Fred sings the second verse to the tune of the song's refrain.