Future Ted: [v.o.] That's a funny story. Marshall was fed up with his job at GNB and was thinking about leaving it all behind, so he and Lily agreed he should wait for a sign from the universe to tell him what to do. Then one day...
[flashback: Marshall is on the street and sees a strange looking ambulance drive by. He notices a stop sign and looks across the road and sees an old fire house that's for sale:]
Marshall: Of course. It's so clear. It's been right there all along. I have to call Lily. Excuse me. Excuse me, sir. I'm sorry, but, um, can I please borrow your... Ernie Hudson?
Ernie Hudson: Yes.
Marshall: Can I borrow your phone?
Ernie Hudson: Who you gonna call?
[present:]
Robin: And did Marshall become a Ghostbuster?
Marshall: That firehouse is still for sale.
Lily: Even Ernie Hudson begged you not to go through with that.
Marshall: Ernie Hudson is a coward!
Lily: [gasps]