Star Emma Kenney told ET that Broderick was a "trooper" joining the show on the Halloween episode!
The Conners certainly know how to do Halloween right!
The iconic TV brood celebrated their favorite holiday during Tuesday's all-new episode -- the third of the spinoff show's new season following the cancellation of Roseanne and the firing of Roseanne Barr over racist tweets earlier this year -- with each family member going all out in their creative costumes.
The episode, entitled, “There Won’t Be Blood,” kicks off with the family -- minus Darlene (Sara Gilbert) -- entering a Halloween-themed Instagram contest with their epic outfits: Becky (Lecy Goranson) as Sharknade O’Connor, Dan (John Goodman) as Napoleon Blown-Apart, Harris (Emma Kenney) as Lizzie Boredom and more.
Since Barr's departure, there have been some additions to The Conners cast, with the introduction of Darlene's new love interest, played by Justin Long, in last week's episode. This week, a second Conner woman was courting a new man, as Jackie (Laurie Metcalf) introduced the family to her new fellow, Peter, played by Matthew Broderick.
"Matthew was so great, so funny," Kenney told ET ahead of the episode. "I was dying watching him. [He] and Laurie have a great dynamic."
Peter, however, lacks much of Broderick's real-life charisma. He's unemployed, and a bit of a dullard, with a master's in medieval culture and a series of Halloween "fun facts" that are anything but.
"There is this one line in the episode... where Aunt Jackie is asking Dan, 'What do you think about him, what do you think about him?'" Kenney recalled. "He's like, 'Well, I've only known him for a little bit, but I know a lot about him,' something like that. It is just so funny and that kind of sums it up."
The actress also praised Broderick as a "trooper," for making his debut during the Halloween show, and spending hours in the makeup chair for the prosthetics necessary to play Peter's head-scratching costume: Descartes' theory of mind-body dualism.
"Matthew's costume is this philosophical mind game, I don't know how to describe it at all," Kenney laughed. "But it was really cool to look at and watch him get done in the makeup trailer... He was there for a long time, he was a trooper."
One person who was left in the dark about Broderick's role on The Conners, however, was the actor's real-life wife, Sarah Jessica Parker!
"He didn't tell me that part," Parker hilariously revealed to ET's Nischelle Turner on Monday, when she discovered her hubby was playing Jackie's love interest. "He told me he got to work with Laurie Metcalf. He loves Laurie Metcalf. We all love Laurie Metcalf... But we don't talk about work much."
See more from Parker in the video below.
RELATED CONTENT:
