This kind of kawaii collectible reminds me that not everything we do (or buy, or think...) has to have deep meaning. Why not keep a plush Smile Slime around. (I happen to have a Smile Slime paperweight.) I've been rather charmed by the cutie-pie culture here, the trend toward the adorable that compels grown men to hang a little Snoopy or Pooh Bear on their mobile phones, young (childless) couples to make a date out of Tokyo Disneyland, and big high school students (or were they 20-something salarymen, in weekend casual?) to play for the better part of an hour with my primary school-aged children on the Bouncing Dome at Showa Kinen park.
For whatever it's worth, the Smile Slime line of toys and pencil cases and you-name-it available at KiddyLand and elsewhere is based on a character designed by Akira Toriyama sometime in the mid-80s for the popular Dragon Quest videogame series. He's supposed to be a drop of water, so as an enemy, he's pretty weak, but he was so popular he later became star of his own spin off game, Dragon Quest Heroes: Rocket Slime. Shall I go on?