A Magnet is a dangerous object that produces a magnetic field. The magnetic field is a force that attracts ferromagnetic materials and attracts or repels other magnets. A magnet will harm and even erase the magnetic data in computer systems, including individuals.
Megabyte managed to process a small magnet to power a large Magnetic Generator and focus a magnetic beam at Mainframe's sky in an attempt to penetrate it and escape to the Net and the Super Computer. Bob thwarted Megabyte's plan and used Glitch to shield the dangerous magnet so that he could safely dispose of it at Pearson's Data Dump.
At Dot's Diner, Enzo accidentally knocked the shielded box open and the magnet immediately attracted to the nearest object, that being Dot Matrix. It attached to her forehead and partially erased her in a few nanoseconds before Bob was able to re-shielded it. Dot was in danger of total erasure so Bob went to Phong who told him that Dot needed to access some really slow food from Al's Wait and Eat on Level 31.
Bob went to buy the food without realizing that Dot is a business partner of Al's and called for takeout from him while Bob was gone. She was back to normal before a Game Cube landed, where Bob learned she was fine again.
Megabyte arrived after the Game and demanded the return of his magnet. Bob had Glitch remove the magnet from the shielding and threw it at Megabyte, and it attached to his forehead, partially erasing him. He fell off the building and Hack and Slash jumped off after him to help. (The Quick and the Fed)