This came up in another discussion, but I didn't want to go off-track.
The graphic novel Parallel Lives showed what Peter & MJ were up to before they met one another. An issue of Untold Tales of Spider-Man from Mary Jane's perspective made it canon.
Paralel Lives revealed that Mary Jane had learned that Peter was Spider-Man on the night that Uncle Ben was killed, so that when she made her iconic debut at the end of Amazing Spider-Man #42, it came after years of wrestling with the implications. In every single exchange between Peter & MJ, she knew his secret identity.
There have been some arguments about the story in the past, and a thread that went on for several hundred posts that got wiped in the forum reset a few years back.
I think it was a mistake since it changes the context of Peter and Mary Jane's relationship in ways the original writers didn't intend for minimal gain (that Mary Jane always knew that Peter was Spider-Man has only been referenced a handful of times- it is telling that there have been no flashbacks to Mary Jane's point of view of the Lee/ Romita era taking this new information into account) but I know there are different perspectives.
What are your views?