Mario Lopez steps in as guest host on “The Ellen DeGeneres Show” this Thursday and Friday and what better way to kick things off than with a reunion between A.C. Slater and Kelly Kapowski?

The 44-year-old “Extra” host is joined by his former co-star Tiffani Thiessen for a “Saved By The Bell” reunion on Thursday’s edition of “Ellen”. The pair reminisce about their time on the hit ’90s sitcom while they make recipes from Thiessen’s debut cookbook, Pull Up a Chair: Recipes from My Family to Yours.

“Oh my God, I can’t believe I’m that old,” Lopez says. “I thought it was 20 years — it’s 30 years since ‘Saved by the Bell’!”

“We are old, we are really old,” Thiessen adds.

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“Saved By The Bell” premiered back in 1989, and since that time, Lopez and Thiessen have both become parents, and their children are now starting to watch old episodes of the Bayside High sitcom.

“Harper started watching it a tiny, tiny bit,” Thiessen explains. “I was okay with season 1 but after that kissing started happening and I was like, ‘No, no, no we’re done.'” The former “Beverly Hills, 90210” actress says that her daughter is only eight and so will have to wait a “few more years” to watch the rest.

Lopez’s kids, on the other hand, are not big fans. “My kids have given it a shot — not feeling it!” he reveals. “‘Daddy, why is your hair like that?'” he said, imitating his kids’ reaction to the show.

Thiessen says that Harper was “into it” and wanted to keep going. “She was so into you and Mark-Paul,” she said, referring to Lopez and Mark-Paul Gosselaar’s character Zack Morris. “She’s so boy crazy already, I have some trouble.”

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Elsewhere on the show, Lopez talks to “Transparent” actress Kathryn Hahn about her new children’s book, My Wish for You: Lessons from My Six-Year-Old Daughter, and how her daughter inspired the story.