With Butterfree, it was just a lucky catch. And Satoshi treated the bug so well that it liked him. Pidgeotto was his only true capture, if you think about it. Bulbasaur chose to battle him.
Eh, aside from the other problems with this episode already stated, my other problem with this was that Bill talked a little too much. He grated on my nerves. I'm sorry for saying so. Please don't shoot me.
Eh...just had to get that out.