Let me get this straight... So you put the thing on, sneak into the persons city, and then a bunch of men run out of the horse screaming and waving sharp objects at people?
Yeah... it's not a great metaphor is it? best to keep things simple: https://www.youtube.com/watch?v=BCGD3UjLFA4
to be fair, "trojan" doesn't necessarily refer specifically to the horse; it's just the term to describe someone or something from troy. maybe that's where the trojan factory is, after all. also, a more accurate trojan horse metaphor would be that you put on the condom so that the woman takes your penis inside her, and then the condom opens up and all your sperm run out and attack her eggs.
