Pocket Monsters Pikachu

Normally when under the effects of Toxic ("Bad Poisoning"), your Pokemon takes incrementing amounts of damage: 1/16, 1/8, 3/16, and so on, of their max HP. You can negate this by switching out; when the Pokemon returns, it will only be taking a flat 1/8 damage like regular Poisoning.

First, assure no save file exists on your game; if it does, hold Up, Select, and B at the title screen and clear the file. Start a new game and do the usual introduction, but choose "ASH" for your name and "BLUE" for your rival's. When given control, walk downstairs in your house to the tile north of the eastern tile of the entrance mat. Open the menu and then save the game. When you select "YES", very quickly thereafter (the timing can take several tries), turn off the console mid-save. (The timing is between the text box with "YES"/"NO" disappearing and the save confirmation message changing.)

If done right, you can access your file and go into the Pokemon menu, but it's blank and extended beyond 6 Pokemon. Grab a Pokemon between slots 1-9 (those immediately on-screen) and swap it with slot 10's Pokemon. Take slot 11 and switch it with slot 9. Go to your Items menu next, and hold Down until the cursor stops flashing. Hit A and glitch the menu, then hit Down, A, Down, A in that order. Now look down the list for a Master Ball. Go down one more item and press Select. Scroll down until you see another Master Ball, and press Select to swap it with the item you grabbed. Now, toss 68 of that item. Exit the menu and then exit your house to walk straight into the Hall of Fame! You'll get the game completion scene as normal, and often have more than 150 Pokemon in your Pokedex!

Leech Seed is a move well-known for absorbing 1/16 of the target's HP and healing the user of the move by the same amount. However, you can actually boost this damage through the unintended effects of Toxic. When you use Toxic to Badly Poison a foe, and then use Leech Seed on them, Leech Seed's damage will also increment: thus, you regain 1/16, then 1/8, then 3/16, then 1/4, and so on, of your HP. Toxic will also be taking effect in this time, dealing the same amount of damage. In other words, you not only regain tons of HP, but also double the damage of Toxic, from one point of view.

To get onto the Cycling Road without needing a Bicycle, simply hold Left while the guard warns you that you must have the Bicycle to enter Cycling Road. (If you already obtained the Bicycle, this still works if the Bicycle is in the PC.) In doing so, you will bypass the guard; if you continue onto Cycling Road, you'll still ride a bike.

In the Japanese releases of Pokemon Red, Blue, Green, and Yellow, as well as all versions of Pokemon Gold, Silver, and Crystal, there is a glitch involving Substitute - no matter the accuracy of the move, if it is a move that absorbs HP (e.g. Absorb, Giga Drain, Mega Drain), the move will have a 100% chance to miss!