A mischievous diaper-clad chimp “christened” yesterday’s “Today” show 50th anniversary special.

Jonah, a six-year-old chimpanzee, appeared to fill his diaper while sitting on host Katie Couric’s lap – and then repeatedly got frisky with Matt Lauer and news anchor Ann Curry.

Jonah seemed especially taken with Couric, who recently signed a $65 million, 41/2-year deal with “Today.”

Later, at a luncheon to honor the show, Jonah’ low-jinx was the highlight of table talk.

“Jonah the chimp and I are going to have a baby,” Couric joked with the luncheon-goers.

Earlier, in the final moments of “Today” as Couric toasted a group of past and present show staffers, the chimp tried to pull a glass of wine out of the hands of frizzy-haired contribu

fused his advances, Jonah banged a

tor Gene Shalit. But when Shalit re

nearby table with his fists.

This isn’t the first time Jonah has gotten himself in a pickle.

The popular primate, who played Pericles the astro-chimp in Tim Burton’s “Planet of the Apes,” is rumored to have taken a swing at actress Helena Bonham Carter while the movie was being filmed.

Besides Jonah, the “Today” show’s 50th anniversary was chock-full with visits from former regulars, including Barbara Walters, Hugh Downs, Joe Garagiola, Jane Pauley, Tom Brokaw and Bryant Gumbel.

But Jonah’ appearance yesterday’s was a nod to the one of “Today’s” original co-hosts, J. Fred Muggs, a chimp who became the trademark of the show from February 1953 until March 1957.

Muggs was paired with original host David Garroway in an effort to boost the ratings. As a result, Muggs became one of the most popular animals to ever appear on television.

Muggs is now about 52 years old and retired in St. Petersburg, Fla., according to NBC.