Thiessen showed Lopez how to make a "boozy date milkshake" with fresh dates, milk and rum. The actress will release the cookbook Pull Up a Chair: Recipes from My Family to Yours in October.
"I am so proud of you. You're a mom, you've got two beautiful kids, and you've got this passion for cooking," Lopez told his former co-star.
Thiessen is mom to 8-year-old daughter Harper and 3-year-old son Holt, while Lopez is dad to 7-year-old daughter Gia and 4-year-old son Dominic. The pair said their kids have watched some of Saved by the Bell.
"I was okay with Season 1," Thiessen said. "But then, after that when kissing started happening, I was like, 'No, no, no. We're done.''"
"My kids have given it a shot... not feeling it," Lopez added. "They're like, 'Daddy, why is your hair like that?'"
Lopez and Thiessen played A.C. Slater and Kelly Kapowski on Saved by the Bell, which had a five-season run on NBC from 1989 to 1993. Thiessen said in March that working on the show Alexa & Katie has brought back memories of her teenage years.