I really wanted to like this one, but too much just fell flat to me.
The story was overall fine, if not terribly original. The pacing and such got off to a fairly quick start (after the weird vegetable thing) and each act was separated well. If there's one problem that hardly ever surfaces on the show now, it's relying too long on one plot point (or shoving in a quick, random act 3 like in S10-11). Even so, the episode had a few other problems.
The characterization of Captain Wacky was just over-the-top, I thought. Some of it was funny (a few scattered lines here and there), but he was usually just angry and violent. The reasoning of him "doing it for his daughter" kind of softened the irritation factor a bit, but when he's punching out a guy for not placing the right light setting, or strangling the Squeaky Voiced Teen over a brand of licorice, it's just too much. Otherwise, I did like Lisa's performance (musical or otherwise), and the ending scene makes up for most of Homer's obnoxiousness earlier. It's no Lisa's Substitute, but it was fairly sweet regardless. I was irritated that Homer didn't get any come-uppance...the show practically promoted the idea that being obnoxious and overbearing is the right thing to do (I'm not asking for after-school special type messages here, but when a character is THAT annoying, I'd like to see some sort of punishment).
The gags were hit-or-miss, unfortunately. Some of the better stuff included a lot of Maggie reactions, Lisa's songs (and the mention of Flanders), some of Krusty's lines, Ralph's A-B-C/Twinkle Twinkle bit, Homer's sabotage song, and the tribute to Snowball. I did think a lot of gags fell flat, like the pointer shooting into Krusty's eye, or Homer with the cookies.
Overall, a fairly forgettable episode salvaged by good songs and a nice ending. C+/B-