Rocking an all-black suit and shades, the actor posed for pictures before fulfilling his role as host.
Before giving a live performance, the rapper posed alongside the model.
The Scandal actress wore a floral dress from Giambattista Valli Fall 2017 Couture.
Not only does Bialik play a scientist on The Big Bang Theory, but she also received a Ph.D in neuroscience from UCLA.
The actress looked pretty in pink as she posed for pictures in a Prada dress.
In addition to being Miss USA 2017, McCullough is a physical scientist.
While posing for pictures on the red carpet, Kutcher put his hand around his wife and told her something that made her laugh.