OK the throwaway is definitely the real punchline here.  I was experimenting with leading and telegraphing in this one.  Doing my best to lead the reader to conclude that the obvious punch wasn’t coming, then hitting you with it anyway.  Dunno if it worked or not, but if there’s a laugh here, it is in the Stephen Hawking joke.

And what the doorman says in panel 2…that’s real Physics man.  I got that out of a current physics journal.