Infinite Uses of Rock Candy
Unconfirmed: To do this glitch, you first need the Rock Candy item in either of the two bottom slots on the inventory of any character. Now, if you use a seasoning while the Rock Candy is on a bottom slot, it won’t go away. You can also use this glitch to gain statistical bonuses at each level up.
by Cactuar (Source)
The Circus Bug
If you keep pressing the left trigger in the right corner of the circus in Threed, you will get a couple messages stating, “No problem here.”; however, if you keep pressing the left trigger it will begin to spew seemingly random characters, appearing to be random strings and alphanumeric dialog screens in some instances. It is even possible to bring up conversation dialogs, and in some cases, even give you items or teleport you.
Warning: It is possible to crash the game doing this glitch; however, there has been no save file corruptions reported.
by Bramblefang (Video), Red South City (Video), and Vaughn
Clumsy Robot Glitch
Unconfirmed: This glitch can be exploited to get twice the experience points for defeating the Clumsy Robot. If Ness makes a Powershield to cover himself and Jeff, and the Clumsy Robot attacks both of them when it has low health, the Runaway Five rush in to shut off the robot after Ness is hit and again after Jeff is hit. This was fixed in Mother 1 + 2, though the scene with the Runaway Five triggers twice you still get the same amount of experience.
The video showcasing this glitch has since been removed.
by Earthbound Wiki (Source)
Glitch Fight after Giygas
After beating the game, you are still able to fight “The Shattered Man” in the Summers Museum if you don’t fight him before you beat Giygas. If you fight him and lose the battle, the game may “crash”; however, more commonly, the game will fade to black but you will still be able to hear the sounds of a dialog menu from the battle. After which you can exit the room you were in to discover some pretty intense graphical glitches for a couple of the museum rooms while you float around dead. If you go to the hospital you can still complete the game normally after this.
by mugg1991 (Video) and chuggaaconroy (Video)
House Glitch
You can use this glitch similarly on normal entrances which will cause the delivery man/customer to not come anymore until he calls you. If you use this on a house you can’t enter and then start a fight in the last possible moment, you will get the graphical bug.
This only works in the US version.
by mugg1991 (Video)
Wow! I’ll have to get my hands on this game!
… Why, yes you do. This game is so much fun!
I know it’s 4 years late, but I wish you luck getting a copy of it, considering they are overpriced. Then again, we have emulators and flash carts. (the N3DS, Wii U and SNES mini are all actually emulators)