According to the recent storyline in Astonishing Thor, the Stranger created Ego, the Living Planet (and his hidden brother, Alter Ego) probably as a scientific experiment. He also gave both planets some of his own personality traits.
So how does this colour the Stranger's relations with Galactus, given that Galactus has tried to devour his creation twice? Is it likely that the Stranger intervened in some subtle way to stop this (i.e. by manipulating events to ensure that Thor was in the vicinity the first time Galactus encountered Ego) or would he have taken the opposite view that facing the threat of Galactus would be a good test for his subject. Perhaps he even led Galactus to Ego in some way.
And then there's Ego's participation in the Elders' plot to kill Galactus. How much did the Stranger know about that and would Galactus want an answer to that very question too?
A possible subject for a future storyline (or some fan fiction)?
How could the Stranger have created Ego? Didn't Ego already have an origin?