In Pokemon Red and Blue, players can utilize a glitch to duplicate the sixth item in their bag. This item duplication glitch has been called the Missingno Glitch because the name Missingno sometimes appears in the name bar.
All you have to do is talk to the old man in Viridian City to learn how to catch Pokemon. After the tutorial, fly to Cinnabar Island and surf along the eastern coast. The glitch should appear in the form of a wild Pokemon battle. Do not attempt to capture this glitch, as it can cause a number of issues.