Not totally arcade related, but an official Parappa music video was dug-up and has a 3D model of the arcade machine with in. www.youtube.com/watch?v=zo21DzAkX9I
Also working on a complete doc of information on NOW!...
Finally! I remember playing Um Jammer Lammy and then hearing about this mysteryous Arcade game, it's really cool to see it being found! Also, in this music video we can see snippets of what's probably an Arcade-only cutscene with Joe Chin at timestamp 0:27. My theory is that this cutscene's audio is this track called "Jam Chin" from the Um Jammer Lammy Make it Sweet! album (You can hear it here, timestamp 29:42) that doesn't appear anywhere in the PS1 game itself, making it possible that the audio was probably heard originally in the cutscene.