I think he thinks it's a 3 stage evo line(poke>bro>king), rather then a split
No, I checked Serebii's Pokedex, Slowpoke does have a split evolution.
If you don't believe me have a look.
That's what the people that posted before you were saying ._.
According to the Pokedex and in the Anime, if a Shellder bites a Slowpoke on the tail, it becomes a Slowbro, if biten on the head, it becomes a Slowking.
I explained how it works in the games in my previous post.
Actually they said it was a 3 stage evolution, I corrected them...
I dont know if this gas been said here yet or not... They said dunsparce is a bug type in a episode called The Dunsparce Deception!?!?