: After Leonard declines, Sheldon expresses interest in donating his "superior" genetic material, but Amy immediately shuts him down.
: This episode marks the final appearances of Zack Johnson and Penny's father, Wyatt. [S12E15] The Donation Oscillation
: Raj and Anu’s canceled bachelor party is repurposed into a group outing on a "Vomit Comet" (a weightless flight) for Raj, Anu, Howard, and Bernadette. : After Leonard declines, Sheldon expresses interest in
: Ultimately, Leonard decides not to go through with it. He realizes he would be heartbroken to have a child in the world that he couldn't personally father. The "Vomit Comet" : Ultimately, Leonard decides not to go through with it
: Penny’s father, Wyatt, visits and expresses his disappointment over her decision not to have children, adding pressure to the situation.
: Bernadette is terrified and tries to back out by claiming it's too dangerous for both parents of their children to be on the flight. When Howard offers to stay behind instead, she realizes he’s calling her bluff.
: Penny’s ex-boyfriend Zack and his wife Marissa ask Leonard to be their sperm donor because Zack is infertile.