First, let me say this episode is not for everyone. It is lacking in most of what serious Batman fan's seek. (then again, this series probably wouldn't appeal to them either.) But if you watched the cartoons New Adventures of Batman (1977), you may have some nostalgic love for Bat Mite, which adds to the appeal of this episode.
The episode is broken up into 3 different (and unrelated) versions of Batman.
In the first version Bat Boy and Rubin, Bat Mite seems to have taken the role of Batman, with a Jerry Lewis style Rubin filing in for Robin. Bat Boy's actions are opposite of what you would expect of Batman making it quite funny.
The second segment isn't all that entertaining, as they attempt to . It seems more like they are attempting to make fun of the short comings of Japanese animation of yesteryear. The story doesn't have much to it, nor is it particularly funny. The one redeeming feature is that the original Batmobile from the 1966 Batman series appears.
The final segment pays homage (or parodies?) the Scooby Doo episode in which Batman and Robin appeared. While I really don't care for Scooby Doo, whenever I saw the opening credits of that show and saw Batman and Robin appear, I hoped it would be that episode. I don't recall many specific details of the original show, but they captured all the elements, especially the look of the Joker and the Penguin as they appeared in the original episode. It's always great to hear Frank Welker reprise his role of Freddy, but it's too bad Casey Kasem was unable to provide the voice for Shaggy, who sounds slightly off.