It will evolve into Yadoking. Go to Saffron City before fighting Sabrina. Challenge Sabrina to discover that her Mr. Mime is female. When you go to Enjyu City, go to the tower and your rival will appear, but will not battle. However, if you first heal your Pokemon at the Pokecenter, defeat the Ghost Gym Leader, and then go to that tower, your rival will talk to you and fight.
Monorail ticket Go to Saffron City and talk to the girl copycat.
Fly to Vermilion City and talk to everyone in the house where you received the bike voucher. Someone will give you the Clefairy doll. Take it to the copycat to get the monorail ticket. He will give you the S.S. Anne ticket. Go to the city where the Gym Leader was first not there.