I've been thinking about this lately
I was thinking about “How would macroscopic aliens actually look?”
Obviously they probably wouldn’t look like green humans, but I also don’t think they would necessarily look completely different from life on Earth.
A lot of the features we see in animals exist because they’re good solutions to certain problems. If you need to move around on land, you need some way of supporting your body and pushing yourself forward. That could lead to something resembling legs, even if the actual structure was completely different from anything on Earth.
The same could probably apply to other things too. An alien might have eyes that work completely differently from ours, but if it needs to detect light, some kind of light-sensing organ would probably be useful. If it needs to grab things, it might evolve some kind of limb or appendage for that.
I think this is where convergent evolution becomes interesting. Earth already has examples of unrelated organisms evolving similar solutions, like wings in birds, bats and insects, or streamlined bodies in fish and marine mammals.
So I wonder how much of an alien's appearance would actually be determined by its evolutionary history, and how much would be determined by the environment and the problems it has to solve.
Maybe aliens could be very weird, but still have some features that immediately remind us of Earth life simply because there are only so many practical ways to do certain things.
Sorry if this is kind of obvious, I just wanted to bring it up.