Rumors your friends/others told you.

I think we have all been told an endless numbers of "pokemon cheats" over the years.
The one with Mew under the truck at the SS Anne port is the most famous one i guess, but i also remember friends teaching me these buttton combos to catch any pokemon with any pokeball, or having to hold B to decrease any damage you take. I actually still do hold B when being attacked out of habit.

The truck-trick with mew in R/B/Y... also, alternating hitting A and B when the Pokeball was rocking back and forth. Insta-catch, right? :P

Back when I was playing Gen 1 for the first time, someone told me that if I level up my Pikachu to level 100 and show it to the father of the girl who wants a Pikachu in the Pewter museum, he would give me Mew... to my defense, I did it not because I was gullible, but because I wanted to prove the guy who told me this wrong :) .

I remember there were other rumors that involved leveling up a certain Pokémon to the level 100 and speaking to a particular person... I tried two or three more, then gave up. To me, these were the worst :D .

Back in Pokemon Silver, one of my friends told me I had to use earthquake to collapse Ice Path clearing the way and allowing me to stroll on out of the cave ..... and I actually tried it. :L

also @deftrance, That A+B button combo was a insta-catch for sure! xD

I was told that Rayquaza has such strong power that it would use outrage inside a masterball and break out of it. I honestly think my 13 year old friend (at the time) believed this.

My friend told me if you catch a magikarp in the resort area in dp, then use splash while battling in the water, it was a OHKO.

Yeah i was told that Splash sometimes OHKO as well... :/ tricked me good and proper.

I was told that in Pokemon Yellow, you could evolve your Pikachu (which refused to evolve under normal circumstances) by getting it to level 100. Also, one of my friends believed that shinies could be found in First Gen, and a playable female character was unlocked by beating Yellow. I admittedly fell for the first one, but the bottom two sounded suspect even to my incredibly naïve 12-year old self.

Mew under the truck and Deoxys on the moon were the biggest ones for me. The Mew one I was young enough to actually believe and, since this was before the advent of the internet, I was naive enough to actually try it. The Deoxys one I believed for about 5 seconds before realising that places like Serebii would have been allllllll over that. Still, rumours like this can often be fun for 5 seconds or so! :D

I'm not sure if it counts since I was the one that started it, but I told my friend when I was a kid if you healed at that old lady's house in Pokemon R/S/E (her house was right above the sandstorm area) that she'd give you a Rare Candy. Friend kept healing over and over until I admitted it was a lie. xD;