Broccoli is a vegetable that is a hybrid of cauliflower and rabe. Broccoli is made when a daddy cauliflower loves a mother rabe very, very much and... wait. I shouldn't be the one telling you this. Go ask your mom.
Anyway, when the Earth was young, about 800 years ago according to Intelligent design, the dinosaurs were tired of eating leaves from these plants called cycads. Sort of like what ferns look like today, but taller. They didn't like broccoli except for decorative contrast in formal gardens and potted arrangements. And they didn't like rabe, because it sounded too much like "fluorescent police siren". So some smart dinosaurs got together and decided two wrongs make a right and mixed the two together to get broccoli. What? Barney? No, he's a stupid dinosaur, I said "smart". Stop crying, okay. I didn't mean it, grandpa.