Recently, I watched a Pokémon Advanced Challenge episode, which was in Generation 3. In these episodes, before going to a commercial break, you will be asked by ash's voice to see which of 3 Pokémon evolve into another Pokémon, and in this episode, it was which of the three, one of which was Arbok, evolved into Seviper. Now, know this that it might've been that they originally meant for Arbok to evolve into Seviper, but I don't know. Anyways, so when the episode came back after the commercial break, it said, "Trainers, if you chose Arbok, you were right!". Now, maybe it's the fact that they got it mixed up, but I believe they fixed it (so that they are no longer considered to be in the same evolutionary line) when they thought it might bring distress since Jessie used to have an Arbok, before sending it away to save a group of Ekans from poachers in an episode of Pokémon Advanced a while prior. I cannot really tell the episode number due to I think I deleted the recording. (I have dish network also, and they are in a disagreement with tuner network, which, long-story-short, led to me losing Boomerang, the channel I watched this on.) Along with this, I have no idea when or where they decided to get rid of the idea Arbok evolved into Seviper, considering now those two are no longer evolutionally related.