You may have heard of comedian/ventriloquist Jeff Dunham, called “America’s most popular stand-up.”

Dunham’s been riding a massive wave of stardom for years. Sold-out tours. Millions in DVD and merchandise sales. His A Very Special Christmas Special was the most-watched telecast in Comedy Central history, and his introduction of the hilariously controversial puppet Achmed the Dead Terrorist is the 12th most-watched video clip of all time (more than 328 million views as of March 2010).

(You can check out the clip here; note there is some off-color language.)

Achmed, the skeletal corpse of a failed suicide bomber, is Dunham’s trusty weapon to combat terrorism with satire. Time notes that Achmed “has not yet come to terms with his demise—he just got a flu shot—and snaps ‘Silence! I kill you!’ at audience members when they laugh, which is pretty much constantly.”

Autistic Teenager Writes Key Joke for Comedian Jeff Dunhams Achmed the Dead Terrorist Routine

So if you’re planning on catching Dunham’s newest Comedy Central special debuting this Sunday night—Jeff Dunham: Controlled Chaos—you won’t want to miss the relatively new character he’s rolling out for the masses…Achmed Junior.

Autistic Teenager Writes Key Joke for Comedian Jeff Dunhams Achmed the Dead Terrorist Routine

That’s right. Achmed the Dead Terrorist has a son.

In addition to being an incompetent terrorist (suffering, as he says onstage, from “premature detonation”), Achmed also has been confessing to audiences for years that he’s a horrible father.

“Why?” Dunham asks.

“Because I took my son to take-your-kid-to-work day.”

Only now we learn, as Dunham teased on Fox & Friends a few days ago, that Achmed’s son wasn’t killed in the suicide bombing…just badly wounded. So dad and boy puppets will be “reunited” Sunday night.

(Check out this clip starting at the 6:10 mark.)

But this reunion may never have happened at all had it not been for the determination, imagination, and sheer pluck of a teenage boy with Asperger Syndrome, a form of autism.

That take-your-kid-to-work day one-liner Achmed’s been flooring audiences with all these years? It’s the brainchild of Matthew Bradley, a Dunham devotee who dreamed up the joke when he was 13 and then sold it to the comedian for $80 in cash and a handshake after an Erie, Pa., tour stop in 2008.

So thanks to Matthew, Dunham not only has a joke with staying power, but also a new character for his act. And thanks to Dunham, Matthew gained a ton of confidence since Dunham bought his joke and started using it onstage.

“It felt good every time I heard it,” Matthew says today, more than three years since Dunham debuted the joke on The Tonight Show with Jay Leno.

It felt good to Sue Bradley, too, Matthew’s mother, who says she had been trying for years to help her son understand and appreciate humor. Nothing worked, she says, until a friend emailed her a clip of Dunham’s stage act with Achmed. When Matthew watched it, he was literally falling out of his chair with laughter.

“I couldn’t believe he was getting the humor,” she recalls of the March 2008 breakthrough. “We played the clip over and over.” Matthew’s not sure why Dunham’s humor worked for him: “I suppose it was just that something finally clicked.”

A few days later Matthew came home from school and told his mom he had a joke—and it was for Achmed. “I thought it was really funny,” she recalls of the now famous one-liner. Matthew’s dad agreed, as did friends who heard the sophisticated quip from the introverted kid. Soon Matthew wanted “the real Achmed” to tell the joke; his mom replied that “you just can’t call up” Jeff Dunham.

Ah, but she forgot that Matthew had already gotten President Bush’s attention.

When Matthew was eight, he wrote a letter to the President of the United States—not an uncommon childhood endeavor—saying he’d like to stop by to say hello. Except Bush wrote back, inviting Matthew to a July 2004 T-Ball game on the White House lawn. There Matthew “threw out the first pitch” by handing Bush the baseball at home plate as Hall of Famer Cal Ripken, Jr. stood next to him.

So the Bradley bunch threw caution the wind again and emailed the joke to Dunham. They didn’t hear anything back but decided a few weeks later to trek north from their home in Pittsburgh to Erie for Dunham’s show on April 24—ironically the real “take your kid to work day” that year, Sue Bradley says.

After the show, the Bradleys hung around Dunham’s tour bus in the venue parking lot with other fans, asked for a photo of Jeff with Matthew, and that’s when Dunham was reminded of the joke Matthew wrote.

“Tell it to me again,” Matthew’s mom recalls Dunham saying. After Matthew told Dunham the joke, he asked, “Did you really write that joke? How old are you?”

Convinced, Dunham told Matthew, “That’s a really good joke. If you send a joke like that to The Tonight Show or David Letterman, they would buy it for about $80—and that’s definitely an $80 joke. Would you sell it to me?”

Matthew agreed, Dunham plopped four crisp $20 bills into his hand (which are still in Matthew’s wallet, by the way), and the pair shook on the deal—with Dunham saying, Sue Bradley recalls, “This is a contract!”

Autistic Teenager Writes Key Joke for Comedian Jeff Dunhams Achmed the Dead Terrorist Routine

He assured Matthew that he’d start using the joke in his shows and to be sure to watch for it. Sure enough, in addition to the Leno and Letterman shows, Dunham used the joke in the June 2008 performance that became his Very Special Christmas Special.

Prior to Dunham’s Pittsburgh gig that September, he gave Matthew 10 tickets so he could take his friends to the show—and that was the first time he witnessed Dunham telling his joke in person. “A laugh riot,” the high school junior remembers.

While Matthew acknowledges that the moment was a “huge confidence boost, it didn’t change me much as a person.”

His mother doesn’t quite see it that way, saying that before being exposed to Dunham’s comedy, Matthew wouldn’t speak much in public and had low self-esteem—he was even bullied at school by classmates who didn’t understand his struggles with Aspergers (which typically limits social skills but often manifests with high cognitive functions). Since his peers learned of his connection to Dunham, however, Matthew has “a nice core group of friends…and a social life,” she says.

“Gaining the humor really turned him around,” Sue Bradley says today. “When you have a child who’s not laughing for the first 13 years of his life suddenly laughing…my husband and I were moved and touched. We could never repay Jeff enough. That he bought Matthew’s joke was just a bonus.”

Matthew has enjoyed some tour-related hang time with Dunham since 2008, and the pair have struck up a casual friendship. Matthew has sent other jokes to Dunham as well, and while the comic hasn’t purchased them, a Pittsburgh comedian has approached Matthew about writing jokes for him.

Matthew says he’s not interested in pursuing comedy writing full time (“It’s just something fun to do every once in a while,” he says). Instead he’s hoping to attend nearby Carnegie Mellon University after graduation to study computer engineering and robotics.

So now that Matthew’s met two famous people in his young life—President Bush and Dunham—which was the cooler experience?

While he’s an ardent Bush booster, Matthew says without hesitation: “Meeting Jeff.”

Even Achmed might agree with that one.