There's a common meme in stories about someone needing a transplant and it unknowingly coming from a loved one or some stupid shit like that.

Here's this is being joked about in the most absurdist way possible: Orchiectomy is a surgery in which the testicles are surgically removed, be it to help with dysphoria in transfeminine patients, get rid of a cancer, get rid of necrotic testicle (like from a really bad testicular cancer), or some other situation I'm thinking about. Now that still leaves the last panel unexplained, and that's where truck nuts come in; in the US, there's a really fucking weird thing some people do which is to buy plastic testicles for their trucks, which hang from the rear bumper, as depicted in the comic.

That's it, that's the joke dissected and dead at this point.