First and foremost, protect your balls.

Super heroes usually have a lot on their plate: anything from saving damsels in distress to keeping the entire world from burning down at the hands of a menace. Granted, Gintoki is no super hero, there are still things a man's gotta protect. Unfortunately for Gin-san, one of those things seems to be his baby-maker. You know, that. If you weren't already aware, the title "Gintama" carries a hilarious and most likely intentional double-meaning. The Japanese word "tama" has two meanings. Depending on the kanji, it can either be read as "soul" or "balls". Which means, yes, when said out loud, Gintama can be humorously misunderstood as Silver Balls instead of Silver Soul. All things considered, it'd be an equally appropriate title.

Gin-chan's stick was useless to begin with anyway. It's much better off rotting and falling off.
--Kagura

To be completely honest, any Gintama fan should've been aware that Gintoki's baby maker would be in constant jeopardy the second the doctor told him his balls would explode if he didn't cut down on his sugar intake (something virtually impossible for an addict like Gin-san). I guess you could say that if all of the other situations don't get 'em, the sugar definitely will. No thanks to Sorachi's ability to cross every line that ever needed to be crossed, we even know that Gintoki grew some "hair down there" around the beginning of the Amanto War, so maybe it's no surprise that there's pretty much no shame in sharing information about Gintoki's private parts when it comes to just about everything else.

During Gintama's Screwdriver Arc however, Gintoki's screwdriver truly takes the spotlight. During this arc, various Gintama characters grow screwdrivers of various drive types on different parts of their body. Shinpachi's finger becomes a screwdriver, the Shinsengumi's entire bodies become screwdrivers. Gintoki is the only one who appears suspiciously unchanged. When he comes out of the bathroom looking particularly distressed however, it becomes fairly clear which one of Gintoki's body parts became a screwdriver. Later on in the arc he proceeds to save everyone with his screwdriver crotch, probably one of the more useful things he's done with that particular attachment. Considering the other times involved pissing profanities onto the Shinsengumi's doorstep or trying to put out a fire, you could say he's a bit delusional about his abilities.

Gintoki: Did ya know? Male cats have a thorn down there. A thorn. Man, that's crazy stuff. Seriously, if I'm reincarnated, I better not be a cat.
Kagura: Like you have any other use for it besides peeing while standing.

On the other hand (and no, that wasn't a pun about how Gin-san gets lonely and censored or censored sometimes), having Gintoki Jr. substituted for a much more useful tool is much better than it being put in jeopardy entirely. Gintoki's been caught on public television with his fly open, gambled away all his clothes, and has even had had Kagura come out of his crotch when she, Shinpachi and Otae were inside his body as stands during their haunted hotel getaway. Sa-chan's also claimed to have caught his "willy peeking out" at the swimming pool with a camera at one point. However, Gintoki's @#^*$cles make a literal appearance during the Diviner Arc. Caught up in a feud between clans, and hoping to help the family of his beloved weather girl Ketsuno Ana, Gintoki attempts to use the "Ketsuno Bomber" by dropping the enemy Doman's onto Gedomaru's weapon. Unfortunately, while the attack hits, Doman disappears midair and causes Gintoki to come crashing down onto the weapon as well, crotch-first. Writhing in pain on the ground, he begs Gedomaru to "drop his balls", and she gives him a smack on the back "of equivalent force"--literally dropping his balls. On the ground.

How far were you trying to push it back down to?! You were going to drop my life before you dropped my balls...Trying to beat me to death? Huh? Hold on a second. Isn't this...you didn't just drop my balls! They're rolling around on the floor!
--Sakata Gintoki, Episode 197
Unfortunately for Gintoki, as he begs the onmyouji to "put them back to their original throne", Doman and Seimei are too busy in the heat of battle to listen to what he has to say. The two continue to argue as they raise and lower Gintoki's @#^*$cles, smash them against the floor, divide them up and do battle with them and even go as far as to name them Yusuke and Sasuke (rival characters and (highlight for spoilers) twin brothers in the manga Sket Dance) as they smash them against one another. Meanwhile, Gintoki screams in horror and attempts to dodge his own @#^*$cles as they fly and ricochet around the room.

I suppose it's ironic that Gintoki even thinks for a second that it's possible his loins could have produced a baby, but there is a baby episode in Gintama which involves a child that looks like the spawn of Gintoki himself. Fortunately for him, the evidence above proves that it's most likely impossible that it was his, and it wasn't. Good luck with that reproducing thing, Gin-san.

If you want to do odd jobs, you gotta be ready for your crotch to do odd jobs.
--Sakata Gintoki, Episode 227