Just watched the Annabelle episode tonight. If I saw it before, I don't remember it, but it's possible that I did many years ago and forgot. It was a pretty good episode in which Nels finally came to terms with his estranged sister.

A few things of note. This episode featured Ken Berry of Mayberry RFD fame. It also featured an older Billy Barty, who often made guest appearances in The Wild Wild West with Robert Wagner, and was also in High Plains Drifter with Clint Eastwood.

Christy learned a valuable lesson on why it's a bad idea to screw Laura in a business deal

Possible continuity:

In the circus big top, we see Nellie and Willie joining in with their mother in poking fun at Annabelle. Yet, when Nels announces to the audience that Annabelle is his sister, you see that Harriet is horrified, yet Nellie and Willie are now clapping and supporting their father's decision to do so.

A bit of trivia:

The lovely (though snooty) Christy Norton was played by none other than a young Wendy Schaal. Most of you might know her today as the voice of Stan's wife Francine in American Dad.