The Big Bang Theory season 10 returns from hiatus on Thursday (27 April) at 8pm EST on CBS Network. Episode 22 is titled The Cognition Regeneration, wherein Penny's ex-boyfriend Zack (played by Brian Thomas Smith) returns and offers her a new job.

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A promo for the episode shows Amy, Bernadette and Penny enjoying a girls' night out at a bar, where she runs into her ex-boyfriend Zack. "Penny, what are the odds of running into you here?" says Jack to which she jokes, "Well, it's a bar. So, pretty good!"

When asked what's new in his life, Zack replies that he has gotten engaged, and revealed that he had a mole that turned out to be "no threat". To which Penny says, "Congratulations... on getting engaged. Good for you." Later Smith's character enquires about Leonard as Penny says that he is working on a government project now.

"We should all have dinner sometime," Penny's ex-proposes and she obliges saying, "Yeah sure. I will check with Leonard." He responds that he'll check with Sara and pulls out his phone and says, "Sara pull up my calendar... [the phone doesn't respond]. It never works on me," he complains and leaves. This leave Penny shocked and she seems to be wondering whether Zack dating his phone. This may not seem such a farfetched thought as fans would remember Rajesh dating his iPhone a few season back.

According to a report in TV Line, Zack offers Penny a job, which she may not be able to refuse, but this does not go down well with Leonard who starts to get jealous. Showrunner Steve Molaro told the outlet, "Penny doesn't like certain aspects of being a pharmaceutical sales rep, like flirting with doctors and fudging the truth about side effects."

Revealing details about the new job offer, Molaro explained, "Zack offers her a chance to head up the sales division of his menu company. She has sales experience, she worked in a restaurant. It's kind of an ideal job, except for the part where she used to sleep with her would-be boss."

The official synopsis for the chapter reads as follows:

Leonard isn't thrilled when Penny considers taking a new job offered by her ex-boyfriend, Zack (Brian Thomas Smith), on The Big Bang Theory.