If I didn't know better, I'd wonder if you were visited by a cuckoo. [He gives the egg a long, long look, clearly surprised as well.] A very big cuckoo.

[If he was prone to flights of fancy, he'd be tempted to believe that one of his people woke up from stasis just to give birth and palm the result off on some random know-nothing. It would at least explain the size of the fuckin' thing.]

More to the point, you don't need to panic just yet. Caring for an egg is a relatively simple task. [One of his best friends is a bird, he's got this!! Because clearly only birds (and fish, and reptiles, and some other shit) hatch from eggs.] One step at a time: is the heartbeat steady and regular?