Who is dating penny smith
There he introduces his wife Marissa and the two surprise Leonard and Penny by explaining that Zack has discovered he is infertile.
They wish to have a child and ask Leonard if he would consider being a sperm donor for them in exchange for a lot of money.
Unnamed father Unnamed mother Unnamed sister Marissa Johnson (wife)Penny (ex-wife) Wyatt (ex-father-in-law) Susan (ex-mother-in-law) Randall (ex-brother-in-law) Lisa (ex-sister-in-law) unnamed ex-brother-in-law via Lisa unnamed ex-nephew via Penny unnamed ex-uncle-in-law via Penny unnamed ex-cousin-in-law via Penny Unnamed ex-paternal grandfather-in-law via Wyatt Unnamed ex-paternal grandmother-in-law via Wyatt Unnamed ex-maternal grandmother-in-law via Susan Unnamed ex-maternal grandfather-in-law via Susan is an on-and-off boyfriend of Penny's who first appeared in "The Lunar Excitation" (S03E23).
He and Penny once got married on a whim while in Las Vegas.
Zack also announces that he has gotten engaged and that his fiancée doesn't want him working with Penny, so no job.
In "The Bitcoin Entanglement" (S11E09), Leonard and Penny visit him to reclaim Leonard's old laptop that Penny had given him years ago.
In "The Fermentation Bifurcation" (S9E22), Penny, Leonard, Howard, Raj and Amy see him again at the wine-tasting house and he takes an interest in Raj's newest companion, Claire. Also, Zack wonders if the guidance system the guys are developing could be use by the military for war causing the guys worries.
Zack also shows them an old video of a drunk Penny made after she broke up with Leonard seven years before.
She did love him, but was scared of a permanent commitment.
He tells that he then got married and purchased a boat.
He invited Leonard and Penny to join him and his wife on the boat.