From the back of the case
"READY TO RUMBLE WITH WARIO?
You'd BETTER be ready, punk! Some evil jewel transformed all of my treasure into monsters, and now I gotta go to this weird world and beat it out of 'em! There are plenty of goons waiting for a shot at old Wario, but don't worry about me, baby--I'm ready to brawl! I'll be throwing punches, charging through crowds, and piledriving ugly mugs right and left. What you gotta worry about is keeping me alive. Can you handle that, or do I have to give you a knuckle sandwich too?
Battle and endless tide of weird enemies with over-the-top moves!
Pummel huge bosses as you scour gigantic worlds for treasure.
Enter bizarre dimensions where you'll have to jump for jewels!
Transfer a sampling of WarioWare, Inc.: Mega Microgame$ to your Game Boy Advance!"