Dermot Mulroney, who is most known for his roles in "My Best Friend's Wedding" with Julia Roberts and Cameron Diaz, "About Schmidt" with Jack Nicholson and Kathy Bates, and "The Wedding Date" with Debra Messing, has been tackling some new territory lately.

Recently, he's been introduced to the horror genre with his paternal role in the spooky "Insidious: Chapter 3," as well as a reoccurring role on Showtime's "Shameless."

The multi-faceted actor spoke with Latin Post about his role in "Insidious: Chapter 3" as well as what it's like on the set of the hugely popular Showtime series that has been renewed for a sixth season in 2016.

"I had a great time on 'Shameless' on set last year. I joined their fifth season and they are having me back for Season 6," Mulroney told Latin Post. "I will start shooting at the end of this summer, among other things, but that's the one I am looking forward to the most."

Mulroney joined the show as Sean Pierce, "a recovering addict and the new manager at Patsy's Pies" where Fiona (Emmy Rossum) works.

"It's amazing, especially to join a cast where most the crew members have been there from year one. Everybody enjoys working for a John Wells production," explained.

"It is a well-oiled machine. They have a rule; you're not allowed to bring your script pages on the set. So that means you're expected to know every line from the first rehearsal. They log in and they start shooting right away," he explained. "It's super-fast, super-challenging and, obviously, if you have seen the show, you've seen the quality in the writing and the cast. So I couldn't believe my fortune."

Mulroney says they called him on a Friday to see if he could start shooting on that Monday.

"I had just two days to even contemplate being on 'Shameless,'" he pointed out, and he couldn't be happier with his decision to jump on board.

Showtime's "Shameless" Season 5 finale reportedly "had all of its characters questioning what they knew about love and relationships" -- "and true to form, to mixed results."

Fiona (Rossum) was given a choice by her musician husband Gus (Steve Kazee) about whether or not she wanted to be with him -- and she ran right into Sean's (Mulroney) embrace, only for him to point out he doesn't want to be the guy sleeping with a good guy's wife," according to The Hollywood Reporter.

Fiona (Rossum) is gradually finding her maturity, "but she's certainly still struggling at the end of the season to choose between Gus and Sean, even though maybe she needs to just choose herself for a change," THR adds.

"We've watched her grow up a bit, and she's a woman now -- she presents herself as a woman -- and so we have to start addressing that. ... We care deeply about her as a character, and so we really want to watch her make that transition into maturity, which is a lot of what Dermot has been doing on the show. He's saying to her, 'You have a lot of potential; you're sort of a fabulous girl, but you're not a girl anymore.' He's pointing out the things she does have real world consequences on the people around her now."

Off-screen the two have a friendly relationship. On Twitter, Rossum confessed that she likes to tease co-star Mulroney about his name.

"Dermot says that in school everyone teased him and called him "Kermit"... So now on set I tease & call him Derm-ee.. not sure why #shameless," she shared, Just Jared reported.

"Shameless" also stars Oscar nominated William H. Macy in the "fiercely engaging and fearlessly twisted series."

"Chicagoan Frank Gallagher is the proud single dad of six smart, industrious, independent kids, who without him would be...perhaps better off. When Frank's not at the bar spending what little money they have, he's passed out on the floor. But the kids have found ways to grow up in spite of him. They may not be like any family you know, but they make no apologies for being exactly who they are."

"Insidious: Chapter 3" is currently in theaters. "Shameless" on Showtime has been picked up for a sixth season in 2016.