The plot of this episode is that The Joker and two of his henchman are using this mind-warping laughing gas to incapacitate the police and the other Gothamites so they can rob them (There’s a scene in which a police officer is too busy laughing to stop The Joker from robbing a jewelry store). There’s an added danger because Batman discovers that lengthy exposure to the gas “will result in permanent insanity” and time is of the essence.
I'll admit there were some downsides. There were some elements which I found annoying (which is why I didn't give it a "10"). For example, there was the weird music playing throughout most of the episode. It was somewhere between catchy and irritating - you know, the kind of music that just gets lodged in your head. Also, some of the action taking place while The Joker and his men were robbing people was a little too bizarre, even for me (the scene with three grown men holding hands and doing a “Ring Around the Rosie” type dance was just surreal). I also noticed a couple mistakes and other things that just didn’t look right (Was Batman welding his gas mask? That’s what it looked like to me).
All in all, however, I enjoyed it. Batman was put in real danger more than once during this episode. It's not a good adventure if the hero isn't challenged, and Batman was. I generally enjoyed the weirdness of this episode (which I'm sure is the same thing that drove some people away from it). What I liked the most was the dialogue. I especially liked the part where Batman confronted The Joker on the garbage scow the villain was using as a floating headquarters.
Joker- Look who's come to trash the place!
Batman- A fitting setting for you, Joker.
Joker- Ooh, I just love to get down and dirty! Okay, boys...it's playtime!