actually the gag has been running for years and starts with the Dr. showing up and giving his name at the start of an episode .... he has done this a few times but not often.
then some human - often a military officer or government official misses the name and asks "Dr. Who?"
Hello I am Dr. J____ S____
Dr. Who ?
I do not recall exactly what episodes have done it but I know that it happened back in the 70's with at least one of the classic Dr.'s
recently I loved the Ep where the lady did not know she was converted to a Daleck Body and made them all forget the Dr. and they all started saying "Dr. Who, Dr. Who......" that one was great!
his name he gave may have well been a fake as it's so very very common