Spider-Man's Marriage

This is one of those tricky ones where an idea was created for an adaptation, then they decided to introduce the idea in the comics as well, before the idea appeared in the adaptation. What makes this trickier is that they tried to have the two storylines coincide.

Since 1977, Stan Lee has written a daily newspaper strip called The Amazing Spider-Man. At some point he decided Peter Parker and Mary Jane Watson should get married in it, and he approached Marvel Comics about them doing the storyline in the comics as well, ideally having them take place the same week.

They didn't happen in the same week, but they did happen close together. In the comic strip, the marriage took place on June 21, 1987:

In the comics, they got married in Amazing Spider-Man Annual #21 (August 1987):

Of course, they're no longer married, which is unfortunate. But it still counts!