Checked in with AC at LGA last week.

Me: Let me give you my Aegean number for miles credit.
Air Canada Ticket Agent: What's Aegean?
Me: A Greek airline.
TA: Oh, we give miles on AC, UA, us, co, lh and a few others.
Me: Aegean is one of the few others.
TA: Sir, I've never heard of them.
Me: Let me give you my number and let's see if it takes. [I read the number from my Blackberry.]
TA: [Unnatural pause.]
Me: The IATA code is A3.
TA: Thanks. Lets see if it takes.
TA: Wow. It even thinks you're an elite.

I took my boarding pass and was on my way.

Similar challenges checking in for a CA flight (departing PEK), but I attribute that first to language, though I suspect if that ticket agent understood me, he would have also disputed their *A participation.

I will have the A3 gold card after one more *A flight and will start actually carrying the card for easy lounge access.

I kind of look forward to the funny reactions to trying to get my points credited to A3 now.