In one episode we see a Klingon taking a piss in an alley and there are two streams. You probably shouldn't cross the streams.
Anyway, this obviously means that there are 2 dongs. This fits canon where Starfleet Medical officers (Definitely Crusher, maybe McCoy as well. I'm not gonna look it up.) have repeatedly remarked on the amazing Klingon physique and how many redundancies it has. (ref TNG 516)
It also makes you wonder about Worf's relationship with Dax (Spoiler I guess? I mean, that show is 20 years old by now).