Here is the secret way to get porygon!
1. get a few pokeballs, ultra balls, great balls, whatever.
2. go to Mr. Backlot's house.
3. SAVE BEFORE YOU TALK TO HIM!!!
4. after you saved the game, talk to him.
5. say yes to the first 2 questions.
6. he will say there is a rare pokemon in the garden, if it is not porygon, shut it off and talk to him again.
7. repeat this process until he tells you there is a porygon in the garden.
8. once he has told you, go into the trophy garden.
9. find one, but use a low lvl pokemon or you will kill it.
10. once you catch it, give it an Up-Grade that you got from professor Oak.
11. trade it to someone.
12. once your porygon evolves, tell your partner to trade it back, then you will have a Porygon-2!
13. according to the National Pokedex, there is a final evolution of Porygon.
14. attach the dubious disk to your newly obtained porygon and trade it back to your partner.
15. tell them to trade it back again.
16. after that, you will have the final evolution of Porygon, Porygon-Z.
This actually works!