(Disclosure/Reproduction)
In the first season, but at the time, nobody noticed. In the ninth episode, “Belly Full of Turkey”, Ted (Josh Radnor) is at a strip club and meets a dancer named Tracey. When he finished telling this story, in his voice-over narration for his future children, he concluded: “And he was so, children, that I met your mother“. The two shout «O what?!” in complete surprise, and Ted from the laughs and admits he’s joking.
At the time, everyone thought the children’s shock was due to the «revelation» that their mother might have been a stripper. But what no one noticed is that for them to think that Ted was serious, their mother really had to be named Tracey. In fact, her name is Tracy, as revealed in season nine. She was the stripper’s namesake, justifying the children’s enormous fright.