[Casey considers that.]

He didn't sound like he was joking. He did all the same stuff he always does when he's making something really cool. [Pulling all-nighters, holing himself up in his lab for days, talking cryptically about this or that, bragging about his genius once he hit some kind of breakthrough. Then the nonchalance with which he announced the project's success.

If this is important like that, it's definitely not a prank.]