Bartcode
Wikisimpsons - The Simpsons Wiki
The Bartcode was a special barcode on the third version covers of Simpsons Comics #1, Bartman #1, Itchy & Scratchy Comics #1 and Radioactive Man #1.
The first four Bongo Comics issues released were released in three versions. The first versions would have a special feature, such as: a poster, a silver cover, or a glow cover. The second version had a standard barcode. The third version had a part of Bart's head where the barcode should be.
However, the second version of Bartman #3 had another Bart code, as did another version of Simpsons Comics #3. However, it is unknown if any other comics had other Bartcodes to complete the second release.