I can remember fully, but it was along the lines of, "Catch a Sunkern, raise it to level 50 WITHOUT evolving, Fly to Azalea Town and press A at the shrine until Celebi appears."
It's amazing how many stupid methods there are for Mew, unlimited items, fake Pokemon, and the like.
EDIT: Oh, R/B/Y/G thread. How about, "Train Missingno., teach it Fly, Fly to all the cities in reverse order six times, and when you get to Pallet, You'll find a MEW in your room."