I've searched everywhere, I can't find a question matching this one. I now know how to get it in Black/White, but what about Black/White 2? I want is for Mega Kick! It reminds me of a certain moderator I know. ;) And uh, I WANT MY SNORLAX!
Munchlax: Trade, transfer or migrate it from another game. It cannot be found in the wild.
Snorlax: Not found in the wild either. Although there is an in game trade you can perform at Nimbasa City (with Yancy/ Curtis).
Yancy or Curtis depending on if you are male or female. However will trade you a snorlax for more info click on the links.
The only way to get him in-game is to call yancy or curtis 30 times, after you have beaten the elite four, and she will offer to trade Pokemon once a day. On the ninth time trading she will trade you a level 50 snorlax. You can trade her any Pokemon for his/hers.
Here is more information: http://bulbapedia.bulbagarden.net/wiki/Yancy