After you talk to Steven in the silph co. in saffron city, you go to copycats house and she will ask you to find it. Go to the poke-fan club in vermilion city. There will be a sailor on the couch. talk to him and he will give you the lost item. Go back to copycats house and give her the item, and she will give you the magnet train pass which you can use in the ticket in the magnet train station in Saffron and Goldenrod City.
(P.S. you can't talk to Steven until after you beat all 16 gyms and defeat Red at Mt. Silver)
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after you get the magnet train pass use the magnet train
get clafairy doll for copycat girl in saffron
go to magnet train manger and ask him to give you a train pass
you can ride the magnet train
you go to the Pokemon tower
You can use it to take the magnet train to kanto I think.
You can now use the train from kanto to johto.
you have to find copycats clefairy doll give it to her and she will give you a magnet train pass hoped it helped you out kieran Thompson
You need to have mewtwo to get it
You talk to the copycat girl in the city with the magnet train in Johto and bring her her pokedoll from viridian in Kanto
Get on the magnet train and it will take you to Goldenrod city. You can back and forth between johto and kanto easily using the magnet train, but it's not essential.