This was a pretty dumb episode. The Riddler is a great character in the comics at the moment, but when he was a villain, he was just pretty much a crummy, cut-rate, terrible-gimmick version of the Joker. He could be fun, but he is ill-suited to the BTAS treatment - he should never, under any conditions, be taken seriously. It just comes across as stupid.
This is one area where I think that Joel Schumacher actually was better than BTAS at adapting the Batman mythos. Casting Jim Carrey as the Riddler was inspired - it meant that the character was being played entirely for laughs - maybe menacing laughs, but laughs none the less. I'm not saying that Batman Forever was a good movie or anything (although it wasn't terrible, unlike Batman and Robin), but Carrey did an amazing job at capturing everything fun about the character.
Because BTAS is only concerned with capturing the fun of the Joker, and making every other villain's story into a grand tragedy, the Riddler becomes muddled. I mean, what can you do? It isn't like he's a character that is so lacking in personality that you can basically just graft a new one on to him without anyone minding (Mr. Freeze, the Clock King etc.) but nor is his story inherently tragic; it isn't like it just takes someone like Bruce Timm to actually properly bring that innate tragedy to the surface - the Riddler is no Two Face. The Riddler is just a joke character, like the Joker, but with one fatal flaw - he has a too concrete gimmick. The riddle thing makes any story inherently dumb - you can play it like a threatening joke like in Batman Forever, or like a ridiculous joke like in the Adam West show, but to play it seriously just makes him seem completely bland.
Also, I think that the producers of the show knew this was going to be a fairly crummy episode - the animation is pretty terrible, like they just shipped it off to the least reliable overseas animation studio in their roster, trying to get it out of their hair.