In high school, I saw two different environmental specials on video in science class. One was made by some college, I think. It included a parody skit called "Forward From the Past", where Doc and "Arty" (I think) arrived in a landfill in the future and look at all of the waste.

There was another special, which could only be described as the biggest freakin' crossover in television history. Mother Nature was in the hospital, due to environmental pollution. Christopher Lloyd reprised his role as Doc, arriving in the Delorean with videos of environmental damage around the world - only it's from the present. He says he's been to the future, and it's much worse. The special also included the casts of "Cheers", "The Golden Girls", "Jeopardy!", "Doogie Howser, MD", and perhaps others.

Does anyone have either of these?

I never saw it in school but I remember that a couple years ago somebody posted a clip of Christopher Lloyd in an Earth Day TV Special so this must have been it. I don't remember where that clip was posted or where you can find the whole thing.