A declaration by a famous sleuth. A type of particle. A school where one probably learned to spell this.

Add a letter to my end, would you? I belong to the lineage of a mister; Donald is his name, childish his moniker. He does not reign, no, he does not rule, But he uses lyrics like a tool. Once you know, remove the last; your hand I cover.

Sometimes, I’m a wall. Sometimes, I’m a mouth. Sometimes, I’m a jar. Sometimes, I’m unhinged.

It's a bird... It's a plane... It's ...

I’m a pit that’s not in the ground, on your body, in pairs I’m found. I’m a host for hair and lint, but may raise a stink that makes others squint.