CT When did the “I am your father line” become so famous?

When did Vader being Luke’s father become more famous than who Luke and Vader are and why they’re fighting? When did the, “Luke, I am your father” misquote take off?

 

It's present in the first comic version of TESB, at least. That may be the earliest major example.

 

I think that, the misquote is born out of the fact that the "Luke" part gives the line much needed context for general everyday use. Know what I mean?

 

The whole, "I am your father" line took off in popularity almost immediately. The revelation was such a huge moment, it became an almost instant addition to pop culture. I agree with @jaimestarr about the misquote adding context, but I think the biggest factor is time. When the line roared into pop culture, we didn't have easy access to see the movies repeatedly to ingrain the lines into our brains. So as time passed, the line starts getting misquoted.

 

I was kind of surprised when I got older that many people completely accepted Vader's claim right away; among kids my age the question of whether he lied was taken seriously. But for adult viewers, apparently Luke confronting Yoda about the question was seen by some people as superfluous. Apparenly Lucas included that because he thought children specifically would have to hear it from a trusted adult character to verify that it was true. But in my memory, the status of Vader's claim was an open question to all until Return of the Jedi had Yoda give his confirmation. I wonder if adults were just playing along with us when they expressed doubt. There was a fan letter I read in some magazine where someone argued passionately that Vader had to be lying. But apparently this interpretation was a minority reading among adults. In an interview around the time of ESB's release, Mark Hamill appeared to assume everyone would accept Vader's claim, which he referred to indirectly so as not to spoil it in detail.

 

Lucas meant for Vader’s claim to be accepted as truth, but when people told him, “Vader’s lying”, he decided to include dialogue of Yoda and Obi-Wan confirming it.

 

There was a bit more to that. GL had been talking to child psychologists while writing TESB, to make sure that he didn't traumatize kids with the revelation, and been assured that most kids would probably be able to handle it and those who didn't would likely assume that Vader was lying.
So he was already prepared for that and knew that he would have to confirm it in the following episode.

 

Children understood fine. It's the adults that likely had more problems with it.