Owarai Yowiko no Game-dou: Oyaji Sagashite Sanchoume (KCEK/Konami, 1999)
It's essentially WarioWare, but with a story. You've got the usual GBC overworld with NPCs and shops, etc, and you progress in the plot by finding and winning minigames. Regular WarioWare didn't come out until 2003, so this was relatively early to the genre. It's also notable for having unbelievably ugly character art.
Pachinko CR Mouretsu Genjin T (Hect, 1999)
I couldn't figure out how to get the ball to actually launch in this one. That's okay, though, because pachinko isn't a real game, and every GBC title that tries to implement it ends up being the same thing anyway.
Pachinko Hisshou Guide: Data no Ou-sama (BOSS Communication, 1999)
In retrospect, it was unfair to say all pachinko titles are the same. This one is worse than the others. As if the concept of watching up to 1,250 small and largely non-interactive metal balls do the same thing for who knows how long wasn't bad enough, this takes it further with terrible graphics and a complete lack of music.
Pachi Pachi Pachi-Slot: New Pulsar Hen (Starfish, 1999)
Rounding out the collection of Japan-only gambling titles starting with "pachi" from 1999, we have one that's actually Western-style gambling. But it's just slots, and slots isn't a real game either.
Pac-Man: Special Color Edition (Namco, 1999)
The Ms. Pac-Man version of this came up earlier, and both games share the same critical flaw: you can only see a quarter of the board. Why bother making this game at all if you can't show everything at once?
Paperboy (Digital Eclipse/Midway, 1999)
I had a collection of this game and Rampage on GBA as a kid, and at the time I thought that anything old and well-known must be good, so I made entirely too many attempts to be good at and enjoy this game. Now that I'm older and wiser, I know that Paperboy is actually just a crappy game designed to eat your quarters.
Papyrus (Planet Interactive/Ubisoft, 2000)
There was a Jungle Book game earlier that was developed and published by Ubisoft with almost identical character movement and animation. Particularly given the weirdness of setting an Egyptian-themed game in the country's famous, um, forests, I suspect this used a lot of shared assets. Of course, since the other game was a perfectly decent character platformer, this is as well.
Perfect Choro Q (Electronics Application/Takara, 2000)
Choro-Q is basically Japanese Hot Wheels, except that all of them do that thing where they shoot forward if you pull them back. This game, in turn, is basically Cars a decade early, and the screenshot you're looking at shows golf if it was played by cars. You pick a direction and turn setting to go in, then set a power level and go. I could see this being fun for kids.