Parents of grown children might call college graduation, a wedding or the birth of their child's child their greatest achievement.

For the parent of a 2-year-old, however, learning that your daughter can sing along and harmonize to a song from "The Muppets" ranks up there, as well.

"My Greatest Achievement" is what New Jersey dad Jesse Teeters calls the duet he made with his daughter, Lexie, after she surprised him with her knowledge of " Mahna Mahna," the song made famous by the purple muppet with the wild, orange hair of the same name.

"That song is at the end of 'The Muppets,' which she loves," Teeters, 34, told ABCNews.com today, referring to the 2011 movie starring Jason Segel.

"We rarely get to the end of a movie but I guess she's been watching the end of it ['The Muppets'] on the iPad occasionally," he said. "We had just finished dinner and out of nowhere she did the 'Manha Manha' and I did the 'Do doo be-do-do.'"

Teeter, himself a professional actor, had his wife, Megan, quickly start recording the spontaneous moment on his iPhone and then posted the video to YouTube, describing it as "The culmination of 2.5 years of parenting. Our first duet."

"I had no idea that she was going to go through the whole thing, or that she could," he said today.

Teeters says he's been bringing his daughter along with him to auditions for his voice-over and commercial work since she was a baby, so while he was taken aback by "Mahna Mahna" as her song choice, he was not surprised to see her hamming it up for the camera.

"She's a bit of an extrovert," Teeters said in an understatement. "She likes to sing. She likes to dance. She's a two-and-a-half-year-old girl. "

"She's a happy kid," he said. "We have a lot of fun."