Doki Doki Sasete!! (roughly: Look for Love!) (Vicor Interactive Software, 2001)
You play a girl who has won a spot on a music TV show where all the contestants form a band and then play a concert at, I think, the Tokyo Dome in a year. But this is really an otome, so it's much more focused on how hot the coincidentally all male other contestants are. It's also aimed at kids, so they're all in their early teens. That's a bit weird.
Dokidoki Densetsu: Mahoujin Guruguru (roughly: Exciting Legend: Magical Circle Guruguru) (Tamtam/Enix, 2000)
This is apparently a manga serialized by Enix, which would explain why it doesn't bother with much setup. You're a kid hero because reasons and a creepy old guy sends a girl along with you also for reasons. She only ever addresses you as "Mr. Hero", because, again, reasons. It seems like it's just a visual novel with nice portraits, but it has link support for 4 players and I can't imagine how that works.
Donald Duck: Going Quackers (Ubisoft/Ubisoft Milan, 2000)
Another character platformer, but actually kind of good. Donald is much more responsive than what you usually get from GBC platformers. Maybe that's not surprising considering the studio behind it went on to make games like Beyond Good & Evil and Assassin's Creed IV.
Donkey Kong Country (Nintendo/Rare, 2001)
It's DKC. A bit uglier than it was on SNES, but seems to play well enough.
Donkey Kong GB: Diddy Kong and Dixie Kong (Nintendo/Rare, 2000)
DKC3, but on GBC. This was exclusive to Japan for some reason.
Doraemon: Aruke Aruke Labyrinth (Walk Walk Labyrinth) (Epoch, 1999)
Shizuka's mom found a lamp and used it to make a genie do the laundry, but then the genie was struck by lightning and kidnapped Shizuka. For some reason this means you need to play Lemmings with Nobita as the only lemming. Meh.
Doraemon Kimi to Pet no Monogatari (Doraemon: You and your pet's story) (Epoch, 2001)
Nobita has earned a big ol' 0 on a test and is terrified to tell his mom, but then he finds an abandoned puppy! He rushes home to get it food and your character swoops in and adopts it first. But it turns out the puppy is a demon monster that breaks things in the house, and it jumps out the window and runs away while you're scolding it. Then it becomes one of those "walk around a zoomed out town and talk to people" games.
Doraemon Kart 2 (Epoch, 1999)
Doraemon and friends get in a time machine and go to a land where the king wants them all to race go karts. It's Pole Position, except even harder to control. Mario Kart was right to skip this system.