i cant choose, the doctor, venom, carnage, the dalaks, the tardis (yes it is alive), however cybermen are technically not aliens just humans from the future that had their brains stuffed into metal bodies, and then theirs transformers, those grey tall ones are classic, and i dont know if the monster inside the cat in the uninvited movie was an alien they never mentioned but i think i may go with a classic and say audrey II from the little shop of horrors