The components of "American History X-cellent" work really well. Lisa and Bart have a good 'B' story with great individual scenes (Bart licking Lisa and Lisa's bit about organ donors), and after decades of their own adventures, it's nice to see them acting like kids again. The elements of the 'A' story work as well: Smithers' evil streak is a nice change of character for him; Moe's unintentional influence of the plot to break Burns out of prison (first with the "meaningful eye contact", followed by the "whispered huddle") is a pleasing little nod to all the clichés we knew were coming;  and Burns' experiences in prison amount to good comedy moments.

However, with the abundance of pop culture references - I counted two Stephen Kings (The Shawshank Redemption and The Green Mile), the nod to American History X in the title, and Lisa naming her surviving ant "Annie" (after "Little Orphan Annie") - there's nothing in this episode to make it stand out on its own. At times, it feels more like "American History X-cellent" was written as a pop culture pastiche, set to the obligatory "Mr. Burns turns nice and Smithers turns evil" plot. There's nothing wrong with the concepts, and the execution works more often than not; but by the time the credits roll, it feels like an old dog playing the same old tricks. However, given the longevity and legacy of The Simpsons, the show has earned the right to not have to reinvent itself at every turn. It may be an old dog and an old trick, but it makes you smile nonetheless.

Naturally, by the end of the episode, everything is back the way it was. Burns reigns supreme at the power plant, Smithers is his sycophantic self, and Bart and Lisa are back to bickering. "American History X-cellent" won't be remembered as the best episode ever (or the "Best. Episode. Ever", if you prefer), but it's got enough to be an enjoyable watch, and a worthy addition to The Simpsons legacy.