You’ll get the S.S. Ticket by helping Bill in his home at the end of Route 25, which is just north of Cerulean City. Bill has changed himself into a Pokémon, so you just need to talk with him and then use Bill’s computer to change Bill back to a human. Once Bill is human again, he will give you the S.S. Ticket.
This side-quest can be completed as soon as you reach Cerulean City and make your way through Nugget Bridge.
The S.S. Ticket is given to you by Bill on Route 25, which is north of Cerulean. So there aren’t many prerequisites, except:
- Reach Cerulean City
Getting the S.S. Ticket
Once you’re in Cerulean City, you will see a yellow bridge on the north side of Town. Attempt to walk on that bridge, and when you do, you will be confronted by your Rival.
Defeat your Rival in battle and then continue onward across the bridge.
At the end of the bridge, you will be given a Nugget as a reward for defeating every trainer on the bridge.
The person giving you the reward is a Team Rocket member in disguise, though, so you’ll need to defeat them too!
After you defeat the Team Rocket member, walk up a bit and then start heading east on Route 25.
Keep walking east, battling trainers when you need to, until you reach the very eastern end of Route 25. There will be a small pond and a house here.
Enter the house, and you will see a Pokémon standing in the middle of the room. Talk to this Pokémon (it’s Bill).
Bill will ask for your help changing him back into a human, then he’ll enter one of the machines in the back of the room.
After he enters the chamber, walk over to his computer and press A to turn the machines on.
After you activate the Teleporter’s Cell Separator, Bill will walk out as a human again. Now you can talk to him to receive your S.S. Ticket.
After he gives you your S.S. Ticket, you’ll be able to board the S.S. Anne once you reach Vermilion City.