Originally Posted by
InsaneDavid
For all the Tengen information you'll ever need, click the link in my signature and read my "Titles of Tengen" column in Retrogaming Times Monthly - every title has been covered as the final game, Gauntlet, will be next month. Go back through the archives and check them out.
As has been said, the cases are different because they were unlicensed - some Tengen games were licensed in addition to the unlicensed versions however and they were revised into the normal NES cartridge shape. Tengen games don't seem unlicensed because they work like a normal NES cartridge, without the override switch on the back, or the resetting and load delays that Wisdom Tree games for example have. This is because Tengen reverse engineered and cloned Nintendo's 10NES lockout chip, creating their "rabbit" chip.