In the episode Larry's Bride, the new plaid style curtains, which replaced the original yellow ones were already up. In the next episode, Chrissy's New Boss, the Ropers are shown putting up the plaid style curtains. Was it possible that these episodes aired out of order?

Good catch! In the Chris Mann book, C0me and Knock on Our Door, the air date of "Larry's Bride" was Oct 31, 1978 and "Chrissy's New Boss" was Nov. 14 of 1978. HOWEVER, the official ep numbering has "Larry's Bride" at (0309) and "Chrissy's New Boss" at (0308). So "Chrissy's New Boss" was actually filmed before "Larry's Bride" although they aired in reverse order.