Allison Janney Faces Off Against Her 'Mom' Ellen Burstyn on Season 3 Premiere

Mom launched its third season with Allison Janney faced with meeting her birth mother, played by Ellen Burstyn, and ET was behind the scenes.

Mom launched its third season on Thursday with Allison Janney's character meeting her estranged birth mother, played by Ellen Burstyn, and ET was behind the scenes for the big moment.

On the season premiere, Christy (Anna Faris) and her mother Bonnie (Janney) quibble over the topic of forgiveness when Bonnie's biological mother (Burstyn) pops back up in their lives.

WATCH: On Set with Allison Janney and Anna Faris at 'Mom,' TV's Most Improved Comedy

"I like to think that the heart of the show is truly this mother-daughter journey," Faris told ET, gesturing between her and Janney.

ET has been with Faris since the beginning of her journey to Hollywood stardom 15 years ago. During a recent visit to the Mom set, we showed Faris her first interview with ET from 2000 when she was promoting Scream.

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Faris cracked jokes about her younger self and the black wig she had on at the time.

"It looks like a helmet," she said. "It looks like I could play for the NFL, don't you think?"

airs Thursdays at 9 p.m. ET/PT on CBS.