She's shown in the opening credits!

Yogi and the gang return to Jellystone park to help Ranger Smith win a "cleanest park" contest by the head ranger. Yea, yea.
Lotta Litter causes all the animals to be careless with their trash and litter and leave it lying around.
She does this by making herself look like whoever she is talking to; Magilla, Snag, Huck.
They finally defeat her when several of them approach and she transforms into Yogi Bear with a pink body and wearing a cowboy hat.
Sounds like a crucial plot moment in the Ray Bradbury miniseries "V" with the martians.
Lotta Litter, along with the Prankster and the Greedy Genie and that Smog fellow, are shown in the opening credits and we see Lotta hurled into a garbage can.
What made this cartoon stand out was the voice of Lotta Litter herself.
It was Rose Marie from "The Dick Van Dyke Show". Fun to hear from her in a cartoon like this.
Also keep an eye out for that blonde haired Ranger Smith again. He showed up in another episode.