There a couple of weird secrets in the Red and Blue versions of Pokémon, which you can exploit to get infinite items or catch rare Pokémon. These secrets may be listed here for your knowledge, but all players are cautioned to be careful if they decide to attempt to replicate them: doing the trick wrong could jeopardize your game data. Sorry, Yellow players, but all of these tricks have been removed from the Yellow version.
Infinite Items and the Secrets of "Missing No." and "M-Block"
There are two vertical strips in the Pokémon world where very strange things happen. One is the east coast of Cinnabar Island, and the other is the east coast of Seafoam Island. When you swim around on these thin strips, as close to land as possible, you can run into wild Pokémon from the last area you visited.
Catch Safari Zone Pokémon Easily!
You can use this trick to catch Safari Zone Pokémon without having to use those weak Safari Balls. Just go to the region of the Safari Zone where the Pokémon you want to capture live. Then use Dig or an Escape Rope to warp out of there (or let your time run out) and then Fly to Cinnabar Island (the trick would be spoiled if you got in any battles on the way). Now you'll run into the Pokémon from that Safari Zone region on the Cinnabar Coast, and you can catch them like normal Pokémon, with Ultra Balls!
Obtain Mr. Mime without trading
While in the Silph Tower, after facing Gary on the (top?) floor, you will come out and when you walk down there is a Team Rocket member. If you go just out of sight, directly above this member, then as you walk down into his line of view immediately hit start before he can see you, then use an escape rope. Your start menu will no longer work once you exit the building. Go up to the Dojo and fight the first trainer on the right side, who has a Machop and Machoke. After that go back to Silph and go to the same floor you used the escape rope trick. When you reach this floor, your start menu will pop up. Hit B to exit, and a level 8 Mr. Mime will appear!
Weird Glitches and Other Silly Tricks
You can actually fish in any statue in the game! You probably won't catch anything, but it sure looks weird.
Cut down a tree, save the game where it used to be, then load it up. You'll be standing on the tree.
The hotel in Celadon City is shaped just like a Poké Center. There's even a PC in the usual place—it's just invisible!
Swim up the water on Cinnabar Island, so you'll be right in front of the Gym. You'll see a phantom guy on the roof.
In the basement level of the Red/Blue Unknown Dungeon, you can climb up the small hill next to the item ball marked with a B on this map, even though there are no stairs.
If you name your character DxDyDz (note: the key here is to have the first, third, and fifth
characters of the name be capital D's), you may run into wild Mewtwo while performing the MissingNO. glitch.
Hope I helped :)
Okay, so I didn't type this all out (I'm sorry if this seems like cheating):