The earliest I remember is that episode in, I think, Saffron City, where in the end, a rocket is launched and it flies in the air... I miss that episode, and I barely remember anything about it, really...
I hope this isn't off-topic, but I remember my last episode. The last episode I really watched for an extremely long time was Forest Grumps, with the Ursaring. This episode was an OK one, but after this episode, I wasn't liking Pokemon anymore, and I stopped watching it. In fact, I still rarely watch the show. (but I hear it has gotten better since Johto, so I'll need to give it a chance...)