Alien plants take over the garden!

Onion plants. They look like wierd alien plants to me, with thier clump of baby onions on top. This is my second year growing onions, so I'm a bit new at this. (I'm a bit new at any vegetable!) There is a smaller onion inbetween the alien things, that is growing seeds. Last year I planted seeds from my onion head, which are turning into nice looking onions. But the alien things? What do I do with those? I feel like they want to be planted maybe. I could try eating one.