Incredible Toons is the third game in the Incredible Machine series, and it follows the same guidelines: solve puzzles by building a machine out of different objects.
As you might have guessed from the name, this time there's an overall theme to the game: cartoons. Everything looks more cartoony, some parts being more cartoony than others (a small man running on a treadmill who only runs if he gets food, for example) and the "characters" look and act more like cartoon characters. The basic cat and mouse from the original now behave more like Tom and Jerry; chasing each other, stuffing their mouths with food, getting hit by anvils and so on.
There's not much to say about this game, really: if you've played any of the other Incredible Machine games, you've already played this one as well. There are many more objects this time, though, and the characters' cartoonish behavior does make the new machines and puzzles more interesting, so it's at least a bit more original than any of the other sequels.
There are a hundred different puzzles to solve, divided into four difficulties, and over seventy different "gadgets". Some are the same, some are new. And yes, you can still make your own puzzles or just build random contraptions.
The bottom line is, if you're a hardcore fan of the series or you like puzzle games, then go ahead and give it a try. Just don't expect it to be too groundbreaking.
If you're running on XP or older, or you know how to make these things work, you can alternately download the Windows version from the extras that was provided by Dishy. It's pretty much the same version, but it runs on Windows and has a hot-seat turn-based multiplayer.