Who is a childish and self-centered buffoon who brings various unusual schemes contrivances to everyday tasks?

This sounds like a description of a classic cartoon character! Here are a few possibilities, depending on the specific "unusual schemes" you have in mind:

From Looney Tunes:

* Daffy Duck: Known for his egotism, greed, and tendency to create elaborate schemes that always backfire spectacularly.

From other cartoons:

* Pinky and the Brain: While Brain is the mastermind, Pinky's childish enthusiasm often leads to absurd and hilarious outcomes.

* The Road Runner and Wile E. Coyote: Wile E. Coyote is obsessed with catching the Road Runner and uses countless inventions, often with explosive results, to achieve his goal.

* Dexter's Laboratory: Dexter, despite his genius, can be rather immature and self-absorbed, especially when it comes to his inventions.

Other options:

* The character of "The Idiot" from the works of E.T.A. Hoffmann: This character is often presented as a buffoonish and self-centered figure who brings absurdity to everyday situations.

To give you a more specific answer, please provide more details about the "unusual schemes and contrivances" this character uses!