I would not normaly advertise for a game like this, but I feel this game is targeted toward the wrong audience. The front of the game shows a childish picture, but I, who would describe myself as a "hardcore gamer," found this game very fun and addictive.
I rented this game a couple of days ago, and obviously loved it. Those of you with a Wii should definately rent it at the least.
Features:
Many different minigames, particle explosions, etc.
4 players, can all share a remote, or each have their own (nunchuck is NOT required, but it simplifies the level builder)
Custom levels
Gameplay has it's challenges: not all easy, even though it is aimed toward a younger audience
Plenty of unlockables, (most for custom levels)
Throw baseballs (and bombs) at the animals you hate the most (LOL)
Downsides:
The throwing mechanic is wierd. It seemed to me that I had to release the A button late.
With too many "Blox" on the screen, you will notice a considerable drop in frame rate.
Uses the sensor bar-When using the "Grab tool" and someone walks in front of you, you're screwed.
The official site of the game can be found
here, where you can find videos of gameplay, and browse the features for yourself.
...and that's my rant, I apologize for meh advertising.

Opinions anyone?
Also, to give you an idea of how fun this game is, Felda, his dad, a friend (18 years old), and I played this game for 5 hours straight from midnight to 5 AM, laughing the whole time.