I just looked up Animorphs Episode (insert number here) and checked Google videos. I used to be able to see all of them (or most of them) on YouTube, but they aren't there anymore. And google seems to have a few episodes. Those four VHS tapes are still out there, but the only episode I would recomend watching from those four tapes would be "Not My Problem"--completely contradictory to the canon Megamorphs, but decent compared to most episodes.
If you could only watch one episode though, I would say watch episode sixteen; Tobias.