'This Is Us' midseason finale spoilers: The Pearsons celebrate two early Christmases

It is quite difficult to come to terms with the fact that a full half season of freshman dramedy "This Is Us" is almost here with tonight's midseason finale. The series was just able to deliver week after week that it almost feels like there has been a regular spectacle to look forward to every time an installment airs. But the one tonight is said to going to be in the books especially with the Pearsons celebrating Christmas early.

As like any family show, NBC's latest hit capitalizes on holidays like the recently held Thanksgiving offering that quickly spiraled out of hand following Randall's (Sterling K. Brown) discovery of his mom's, Rebecca's (Mandy Moore), secret. While last week provided some room for both parties to come to terms with what just happened, the drama picks up back this week with the two reuniting over Christmas dinner.

The synopsis for the outing titled "Last Christmas" does not give too much away in terms of what the present day holds for the clan as it mostly focuses on the time jump to the past where Dr. K makes a reappearance. But it seems like fans will be knowing more about William (Ron Cephas Jones) with a special cameo by one of his friends, Jessie. Played by "American Horror Story" stalwart, Denis O'Hare, show creator Dan Fogelman shares that the character will offer a glimpse to how Randall's biological father has lived long before he first met him.

"He's a friend from back before," Fogelman told Entertainment Weekly. "And William on Christmas Eve returns home to take care of some stuff back at home, and through his old buddy, we get to learn more about William. It's not what the episode is about, but because people have been asking, he holds the answer to what has happened to William's cat."

While the writer appears to downplay O'Hare's involvement in the arc of the episode, his appearance still evokes much interest as it is tipped to somehow solidify the story in connection to Randall's eagerness to know more about his father.

The episode is tipped to be an emotional one maybe in ways that fans would not expect given that it is a time for celebration inside "This Is Us" timeline. But with Helen Hunt behind the lens for this particular narrative, it is almost an indication that something pivotal is going down for the major game players of the show. Brown has previously spilled about filming the installment as being emotionally draining so that could be an enough hook for viewers. Moreover, another cameo in "Westworld's" Jimmi Simpson should also be expected and although no additional information has been given regarding this, the actor shared that he will have some on-screen time with Brown.

"This Is Us" airs every Tuesday, 9 p.m. ET.