Is Justin Bieber Cracking Under Baby Mama Scandal? (video) 1Justin Bieber forgot the words to one of the songs on his hit Christmas album Under the Mistletoe on the “Today Show” this week, suggesting the singer may be under stress from his ordeal with alleged baby mama Mariah Yeater.

The case took a serious turn this past week, after Yeater’s lawyer refused to accept a DNA sample taken by Bieber in New Jersey because no one representing the 20-year-old San Diego woman was there to oversee the test.

Wrangling over the test could ultimately send the matter back to court, if the two sides can’t reach an agreement on the examination.

Yeater’s lawyer Jeffrey Leving also beat back faulty tabloid reports on gossip site TMZ and elsewhere that his client is now trying to dodge having her baby tested.

He said she can’t wait for the test, which put the ball squarely back in Bieber’s court.

The teen star tried to go about his business with appearances on the NBC’s “Today Show” and David Letterman’s “Late Show.” But he was clearly off his game.

On the “Today Show,” he forgot the lyrics while singing “Santa Claus Is Coming To Town” in front of a national audience.

The song is on his No 1. Chrismas album.

Bieber tried to cover up by repeating the verse “he’s making a list” several times instead of the correct lyrics.

The 17-year-old stopped singing altogether at one point and danced around to cover for his error.

Obviously, Yeater was on his mind.

Usher, who joined Bieber on stage said Yeater’s claims that Bieber fathered her childs “comes with the territory.”

He should know. Usher’s relationship with TLC member Rozonda “Chilli” Thomas ended in 2003 after she accused the singer of serial cheating.

“Usher did the ultimate no-no to me….I will never be with him again, and that is that,” she said at the time.

Two years ago, he filed for divorce from wife Tameka Foster, after she suffered a serious injury. They have two children together.

Bieber’s other major gaff came on the Late Show, when he bragged that he’d been to all seven continents.

Letterman asked him to name them, but Bieber, a high school dropout, fumbled the answer. The one he couldn’t remember was the most obvious–Europe. Oh yeah, and Australia.