What would alien life look like?

[I_am_not_mafia]

I think to even start answering what alien life would look like would require you to figure out which alien environments could have life evolve on them. We know that there are other Earth-like worlds out there, so we could focus on those and ignore ice worlds, ammonia worlds, moons orbiting gas giants etc even though these could well evolve alien life as well. But then if you look at the history of the Earth, there have been many different periods where completely different life evolved. The first primate-like creature was tiny and appeared just before the KT Impact event that wiped out the dinosaurs. So even if we found another planet exactly like Earth, you couldn't assume that it would have human like aliens. Or even if they had evolved in the past whether they were still alive.