In the episode where Jerry "tanks" his act because he performs before Bania, I noticed this production error:
1) After performing his set, Jerry comes backstage wearing suspenders and having sweat stains by his neck and armpits.
2) Jerry looks through the doorway while Bania begins his set and his shirt is mysteriously MISSING the sweat stains.
3) After Bania's set he sees Jerry by the bar and the NBC execs walk in. Jerry's sweat stains suddenly REAPPEAR.