Homer's half-brother, Herb, shows up after he learns of Homer 'winning' $2,000. Herb wants to invest that money in his new invention which he needs Maggie to help create. Homer didn't actually win the $2,000. It's a settlement from the power plant because he's sterile from working there. The Simpson family will never know that though, not with Mr. Burns ingenious award!
Danny DeVito reprises his role as Herb. This episode was produced because of fan reaction to the season 2 episode, Oh Brother, Where Art Thou, which I've also reviewed on this site. Fans felt like the ending to that episode was too sad. The Simpsons answered with this episode.
I don't think it's anywhere near as good as the 2nd season episode I mentioned above. It still has a lot of charm and some good jokes, particularly with Herb and Maggie and Homer's reaction to Herb's example of an invention. Mr. Burns is great in this episode as well.
You have to see it if you've seen the 2nd season episode, if not, then you should still check it out. The Simpsons was unequivocally must-watch television in the 3rd season and this is the last episode of the season.