Um Jammer Lammy NOW! is the arcade verson of Um Jammer Lammy, which
was originally playtable in arcades across Japan through the year of
1999.
The arcade machines were developed by Namco, running a modified version
of its System 12 arcade platform that allows the game to (partially)
run off a CD drive.
Um Jammer Lammy NOW! has many differences from the original home release of Um Jammer Lammy, most notably the use of guitar controllers specfically made for it rather than the PlayStation's DualShock, Parappa being playable on the 1st stage and many new cutscenes that were never present in the original game.
Following its release, Um Jammer Lammy now was rolled out at arcades and conferences all across Japan, most notably the 1999 Tokyo Game Show, but the only known surviving machine to this day is owned by a British celebrity.
In 2023, Um Jammer Lammy NOW! was dumped and released to the public on the Internet Archive. You can now play it at home through the power of emulation thanks to MAME!