El Penguino developed some sort of "crime-slime" that turned people (and mice) evil, never mind that it was actually a gas, the intended effect was intact. Penguin also managed to land a girlfriend / henchwoman Gigi. Even though she was no looker, Penguin having a girlfriend may be the most far fetched element of the episode that's actually saying a lot considering what transpired. In a classic tale of switching places, the crime-slime somehow doubled as a body swapper turning Penguin into Bat-Mite.
Luckily, even though the Mite got Penguins body, he retained his powers. The evilized Batman and Robin went off to steal a billion dollar "Midas Meteorite" that for some reason was just on display in the city center. That alone sounds like a pretty poor choice by the city leaders. But wouldn't you know Batman was just playing along. I will say that with all its ridiculous twists the episode was kind of fun. If they were going for over the top, they hit it.
Other notable bizarre happenings:
Robin's line "Holy ticklish tackle Batman"
The solid gold meteorite floated
Penguin had a custom penguin boat and car
Episode Count: 0230
Series Count: (13 of 15)