I keep hearing about sequence breaking in gen 1, but cannot come up with too many options. Could veepee find more of them together?
No glitch run, hacks or trading HM slaves from a completed game, let's keep it vanilla.

And a riddle for everyone, if they can't come up with anything: what's the very first thing that joins your adventure in this gen? It's a single Potion inside your computer, before leaving the room.