2 consecutive flubs happen near the end of this episode.
First, as Andre is being thrown out of the apartment by a steamed Ralph, you can clearly hear Andre say: "I'm through, Mrs. Kranston!!" Kranston? Should've been Kramden obviously.
And meanwhile, as Andre is leaving, you can see Ralph's hand coming through the "glass" of the window, still holding the glove as well. And what makes this even funnier is that just moments earlier, Jackie made a valiant attempt to feign glass being present by placing his hands flat against the panes, as if there really was glass in the window. Alas, it all goes out the window, so to speak, moments later.