Eight-year-old Knuckles may not be the most talented pooch, but there is one the thing the Jack Russell Terrier can do without fail.
Whenever he hears the "Law & Order" theme song, his ears perk up and he starts to whimper, then he lifts up his head and chimes right in, singing along to the music with a full-blown wail.
"He's not the brightest dog in the world, but he has this one talent," said his owner, Daniel Serna of Los Angeles. "It's just a funny thing he'll do and he'll do it for a room full of people."
Serna said he noticed it right after he brought Knuckles home years ago.
"The first time he saw the show, he started howling along to it and we just started busting up," he said.
About a year ago, Serna and his wife posted a video of one of his dog's performances to YouTube. That video, "Knuckles The Dog Singing to Law and Order," has nearly 10,000 views.
Asked if he was aware of Knuckles' budding Internet fame, Serna was astonished.
"No… Really?" he asked. "Oh, my God. That's great."
But it turns out Knuckles' performance isn't so unique, and in fact, it may be nothing more than an involuntary reaction -- and the next YouTube phenomenon.
Could Howling Dogs Be Next Internet Sensation?
Much like the recent fascination with the piano-playing cat, a crop of YouTube videos featuring dogs howling along with the "Law & Order" theme song has gained popularity online.
A YouTube search for "Law & Order + dog" generates at least several dozen videos of "singing" dogs like Knuckles.
Serna said that when he and his wife posted the video of Knuckles they had no idea that they had company, and some of the videos were posted as many as three years ago. But as blogs picked up on the unusual doggie dance over the last few days, more owners posted videos of their crooning canines.
A video called "Logan The Poodle Sings to Law & Order Theme" has attracted 36,359 views, and another, "Tug's reaction to Law & Order intro," has more than 19,000 views.
The videos show dogs of every size whining, whimpering and wailing as the "Law & Order" theme song pipes through in the background.
More recent videos feature owners trying to see what happens when they play the song for their own dogs.
But why do some hounds howl when they hear this particular theme song?
Veterinary neurologist Susan Wagner said that, though she wasn't familiar with formal research on the topic, it likely has to do with the higher-register notes in the distinctive theme song.
"Cats and dogs generally don't like hearing high-pitched sounds," she said, adding that dogs often howl to sirens and other higher-toned sounds.
Dogs, Cats Don't Like High-Pitched Sounds
Wagner recently co-authored a book titled "Through a Dog's Ears," which explores sounds that can improve dogs' health and well-being. Her research behind it showed that lower tones and simple music calm canines.
"Different types of music affect dogs from a behavioral standpoint," she said. Classical music arrangements, for example, especially those with lower tones, slower tempos and less complexity, reduce anxiety, she said.
The higher-pitched, upbeat and complex "Law & Order" theme song could have the opposite effect.
"That would be my hypothesis," said Wagner. Though the research hasn't been conducted, she said, based on the reverse finding regarding the lower tones, it seems likely.
But, she added, "I'd hate to do that to them."
For his part, the creator of the "Law & Order" theme song, Mike Post, said he never expected dogs would be "humming along with my tunes."
"I can't believe it. This is the craziest thing I've ever seen in my life!" Post told the New York Post.
"They're not running away from it, they're singing along with it," he continued. "If somebody notices my music and appreciates it, I'm happy -- and if those are very happy canines, I'm happy."