I was just reading through Ego's entry on the Marvel wiki, and I saw several ways we could get a human form Ego.
At one point they said he was formed when a humanoid scientists consciousness fused with a planet, although this was later retconned away.
If they decide to go with this origin, then maybe something happened that the scientist's consciousness splits off into a humanoid body again, or he can switch back and forth between the planet and the humanoid body, or maybe he didn't get turned into a planet until after he got Star Lord's mother pregnant.
It also says that he split off humanoid beings made out of parts of himself that he sent out to conquer the galaxy. Kurt Russel could be one of those beings.
At one point they said he was formed when a humanoid scientists consciousness fused with a planet, although this was later retconned away.
If they decide to go with this origin, then maybe something happened that the scientist's consciousness splits off into a humanoid body again, or he can switch back and forth between the planet and the humanoid body, or maybe he didn't get turned into a planet until after he got Star Lord's mother pregnant.
It also says that he split off humanoid beings made out of parts of himself that he sent out to conquer the galaxy. Kurt Russel could be one of those beings.