I've recently had a fascination with a very obscure Nintendo IP. The brainchild of Creatures Inc., better known for their involvement with the Pokemon franchise, these games are about these small, goofy little guys known as "Chaliens", who come from space. Only one of the three games in this series made it out of Japan, with the only other official trace of this series being the appearance of mascot Li'l Blue as a spirit in Smash Ultimate.
These are the games:
Chee-Chai Alien (Game Boy Color, 2001)
The debut game, Chee-Chai Alien is about capturing Chaliens from real-world life sources via the GBC's infrared port. At the start of a new game, a Chalien named Saraba explains to the player that they need to extract the dark matter from these Chaliens to launch rockets into space. Part of this process involves playing numerous mini-games via collected Chaliens--the most common one is "Kurukuru Battle", but each Chalien's mini-game may vary, with some being exclusive to just one particular Chalien.
As this game relied on the infrared port, which was removed from the GBA, Chee-Chai Alien will lock itself out on such systems, being playable on GBC only, unless a cheat device is used.
Nonono Puzzle Chalien (Game Boy Advance, 2005)
This one's scope is a bit more low-key in comparison to its predecessor, being more of just a mini-game compilation than a Chalien collecting game. At the start of the game, a weird little guy with a star on his head named Hirokacha tells the player how the Chaliens' ship got damaged by a vortex, and introduces them to the gist of the mini-games, each of which involve spinning a 2x2 portion of a tile grid with the A and B buttons. The three mini-games using this mechanic involve preparing food in a microwave, keeping a Chalien on a walk without letting them fall, and a more standard block puzzle-type game, respectively. The latter of these mini-games does introduce some specific Chaliens after some puzzles in the one-turn mode, carrying on a teeny bit of the collector legacy from the original game.
Single and multi-pak multiplayer is supported for this game, and I think there's even some Wireless Adapter support.
Spin Six (DSiWare, 2009)
This DSiWare release takes the puzzle mini-game from Nonono, and mostly reproduces it into a standalone title. That is, it's essentially just Nonono's Spin Six mode. The big deal with this one, though, is that it actually got released in America and Europe in 2010, with the Chalien series getting official English localization, and as such official English names for all the Chaliens featured in the Spin Six portion of Nonono.
Overall, information and enthusiasm for these games is rather scarce, but a fanmade wiki does exist if you'd like to know more.