Pop’n Twinbee on Gameboy was first released in Japan in 1990 then a few years later in Europe. America, sadly, did not see this vertical shooter.
The linked co-op gameplay in this Gameboy version of Pop’n Twinbee is entertaining thanks to the stable connection, quality pacing, and bell power-ups.
Years later, Konami re-released several of their classic Gameboy titles into compilation carts that were only released on Europe, updating them to support the Gameboy Color. Sadly, this re-release of Pop’n TwinBee saw the removal of the 2-player linked co-op mode (I’m guessing to save cart space).