There are some very funny environmental videos on this page.
I love the top one with the boy passing the note in class - promoting recycling.
I was in stitches with some of these Jim Carrey videos, but that man can make just about anything funny. However, the Jim Carrey videos (albeit very entertaining) don't tick the boxes as far as assisting to promote the green cause. Many people (though not me personally) might feel that this video drives a deeper wedge between greenieism, and the mainstream. But we should remember they were made to be funny not to promote a cause, so Jim has succeeded in his objective. Possibly, he is also making a point, that greenies can come across as too intense and opinionated for words, and the average person doesn't want to be made to feel guilty about eating a hot dog. In fact Jim Carrey is indeed a confirmed vegetarian (at last check) so he is probably just taking a dig at those who make too much fuss about the dog ... of the hot variety.
I have come up with a formula for environmentally friendly humour, which am happy for people to enlarge upon, and there are at least four ingredients: (1) the good-will factor - does the video, joke, slogan etc carry good-will input's towards environmentalism itself, as opposed to satirising or lampooning environmentalism as its main objective (2) in the case of videos, are the characters ones we can empathise or identify with (3) does the joke, video, slogan talk up the activity or message being promoted, rather than talking down a specific activity, and (4) is the video, joke, slogan memorable, catchy or uplifting?
I think the recycling video achieves all four of these aspects, it promotes the act of recycling a piece of paper (rather than talking about stopping the waste of paper) it's pro-environmentalism, it is memorable, and also the boy-girl classroom exchange (not necessarily in the form of letters!) is something most of us will have experienced as kids.
Will keep this post short, as it's too late to write much.