Brian Williams' daughter Allison is not daddy's little girl anymore, although you can see her on tv as one of the lead stars of HBO series 'Girls.' And if you are one of the 26-year-old actress' critics who slammed her quick rise to fame, saying that it's all thanks to nepotism and her well-connected background that she landed a lead role for the show, you might as well think again after reading this entire post.

In the series, Brian Williams' daughter plays Marnie Michaels, a would-be singer who is distinctly uptight from the group of four girls. In reality, Allison Williams is also a singer, although not really a recording artist. She starred in a YouTube-uploaded video titled 'Mad Men Theme Song With a Twist,' where she sang Nature Boy to the tune of the hit show's theme song. (An embedded clip is provided below for you to check out Allison's singing voice.)

Fun fact: the musical video helped the actress land the role in her on-going series. Executive producer for 'Girls,' Jude Apatow fortunately saw the video when it aired and asked Williams to audition for the role right away.

On the other hand, although this may sound unbelievable but Brian Williams' daughter is actually far from being the uptight wannabe singer of the show. Allison has actually a credential for doing some improvisations. While still studying in Yale University, she even joined an improvisation group called 'Just Add Water.' She even recently revealed to Yale Daily news that her talent in making improvisations also helped her during her audition for the show. She said she had an improvisation scene with Lena which actually lasted for about ten minutes.

Additionally, this chick also has some sense of humor. If you have been an avid 'Funny or Die' viewer, then you may have seen her performance in episodes titled 'Will & Kate: Before Happily Ever After,' which she reportedly wrote as well. She portrayed the Duchess of Cambridge, who was rather highly concerned about the lighting on William's head.

Another thing you should know about Brian Williams' little (not anymore) girl is that she has always wanted to become an actress ever since she was still on her early teens. However, she revealed to the New York Post back in 2011 that her parents wouldn't allow her to engage into the showbiz industry not until she graduated from college.

Having said all these, it is not surprising that the daughter of Brian Williams is basking under the popularity she established on her own. And just this Monday, she was spotted at the launching party of the third season of her show by HBO and The Cinema Society at New York's Lincoln Center.

At the red carpet, Allison dished to MTV News a few things fans should watch out for in Marnie's storyline.

"[She's a] total and complete mess!" she said. "[Her mom] Evie (played by Rita Wilson) is partially responsible for why Marnie is such a mess. She's not much of a foundation, so when you fall apart and you don't have much of a foundation, you fall pretty hard, I think. [It's] definitely a case of the girlfriend mom, like the cool mom from 'Mean Girls.'"

Brian Williams is a famous American TV producer and anchor of the NBC Nightly News. Meanwhile, Allison's mom, Jane Stoddard, is also a TV producer.