Did John Hancock know when learning penmanship in kindergarten that someday his Feb. 7, 1783 “John Hancock” signed letter would retail for, give or take a few, $50,000?

Debbie Reynolds never signed the Declaration of Independence but did inscribe photos, and they’re yours for a buck. Burbled one dealer gleefully: “Big requests for the oldies. A Sinatra memo was a dollar, but after he became chummy with the president, he soared to $1.25 . . . I get $3 for Fred Astaire.”

Will Ferrell is one of the worst signers. Autograph Magazine says: “He mocks people, taunts and embarrasses them when they ask for autographs.” Tobey Maguire, not so good. Russell Crowe, known for bad boy behavior, segued from 2006’s Worst to No. 10 on 2007’s Best.

Cameron Diaz hit the top of the Worst for years. Bitched fans out when they asked. Told them to f - - k off.

Others not wildly gracious: Joaquin Phoenix. Renée Zellweger. John Malkovich. Julie Andrews. Bruce Willis. Teri Hatcher. Scarlett Johansson. Cybill Shepherd, also not so good. William Shatner reputedly signed his book for $10 per. And that was for a paperback.

Rosie O’Donnell? Snippy. Doesn’t sign. Thinks it’s sad when adults want signatures.

Basketballer/civil rights activist Bill Russell won’t sign. Ever. Supposedly a retiring player wanted the team to sign as a memento. He still refused. The teammate was hurt.

Johnny Depp? An easy signer.

Other nice ones: Damon, Clooney, Nicholson, Travolta, Leno, Rosario Dawson, Katherine Heigl, Dakota Fanning, Stephen King. Richard Thomas signed at a busy flea market. Joan Rivers carries trinkets and distributes them along the way.

Although late for a show, LL Cool J took time. Delighted to oblige.

A young girl knocked on Ewan McGregor’s door. Normally happy to sign, he wouldn’t at home because of the invasion of privacy. She said: “Yeah, I understand but could you just sign this please?” Rumors are he closed the door on her.

After their show, Penn and Teller shake everyone’s hand, chat, write their names. Without changing clothes, they come right out front p.d.q., both still in costume. Once, they wore togas covered in fake blood.

Clint Eastwood never uses the excuse, “Sign one, you have to sign all.” He’ll stay until everyone’s satisfied.

Shaquille O’Neal scribbles an S, a line, an O and a line. Lame as it was, this penmanship sold for $1,500.

Back when her signature meant something, Mary Lou Retton barked to those begging for an autograph that “I don’t need you.” Someone less charming and cuddly as myself might mumble: “Yeah? Well, now she does.”

One fan: Kevin Spacey was “condescending . . . I’m going to believe it was just a bad hemorrhoid flare-up.”

A lifetime ago before cellphones, selfies, Skype, texting, Twitter, iPads, YouTube, Facebook, Bob Hope told me: “I try never to be negative. It will hurt me. I’d never refuse an autograph because that’s bad for me. In an airport, if a fan’s pestering me, I just say, ‘Catch ya later . . . gotta get an airplane,’ and, boom, I keep moving.

“If you’re late for a plane, what they do is start fumbling around with, ‘Do you have a piece of paper?’ You want to kick ’em right in the ass when they do that. And then their pen leaks on you.”

So there was the time a guy wanted me to write my name on his card. I did. When I came back out he asked again. I did. When he wanted a third one, I asked what’s his problem? He said: “If I get three of you, then I can trade for one Seinfeld.”

Another time I wrote my name. The man examined it, said, “Oh, Jeez,” crumpled it up and threw it away. I don’t know who he thought I was — maybe Gilbert Gottfried?

One great shtick is when someone accosts you. You’re late for something. You’re hustling. You’re carrying packages. You’re alone. The person passes you then p.d.q. doubles back, stands right in front of your face, blocks your way and says, “So who are you?” They know they know you. They know you’re familiar. They know you’re somebody. They just don’t know who, where or what. Oy, trust me, it’s very flattering.

No business like show business.