in-love
Explanation
The Joke
A couple stands on a beach at sunset in a romantic scene. The man declares, "I'm so in love with you. The sea, the sand, the emptiness." The woman responds, "Promise me. I'll never forget this moment as long as I live." In the next panel, their child interrupts asking "What are you doing?" The man, now clearly a father, replies irritably: "Making it look like I accidentally let testicular tissue hang out of my open fly while your mom retrieves a ball from your brain." The woman then asks "Oh! Like regular stuff?" and he says "Make up your mind!"
The comic contrasts the idealized romantic life of a couple before children with the chaotic, undignified reality of parenthood. The beautiful sunset promise of eternal romance is juxtaposed against the absurd, gross, and frantic reality of dealing with kids.
The Humor
The humor comes from the extreme whiplash between the saccharine romantic moment and the grotesque absurdity of the parenting scene. The couple's pre-children selves made sweeping promises about never forgetting magical moments, but their actual lives are consumed by the messy, bizarre, and decidedly unromantic business of raising children. The woman's casual "Oh! Like regular stuff?" is the cherry on top -- suggesting this kind of chaos is so routine that it barely registers as unusual.