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I've looked it over again and really, I can't find anything in your character list that is keepable with maybe one exception. To wit:

 Aperitif — only appeared in one episode, best to just mention it in that episode's summary
 Pinians — only appeared in one episode
 Wunny Sharbit — Maybe.
 Melvin, Eduardo, Harold, Sid, Doug, Slouch Potato, Yetis, Alligaturtle — only appeared in a couple episodes
 Caterpillar through Career — background-only characters without speaking roles, not relevant
 Whirrls — only appeared in one episode
 Crocowolf, kangaraccoons — only appeared in one episode. Having seen the latter episode, the kangaraccoons are only a one-shot gag and not relevant to the plot, so they shouldn't be mentioned.
 Batrdrill to end of list — Again, only appeared in one episode each.

The one-shots can easily be mentioned in their respective episodes, but only if they're relevant to the plot (for instance, Aperitif), but the episode plot summaries as they stand are kind of long and overly-detailed themselves. The article as a whole needs a major rewrite to be more encyclopedic. Ten Pound Hammer, his otters and a clue-bat • (Otters want attention) "