When a comic series goes on for a really long time, and characters go through a bunch of adventures that change their story as well as the limitations of their powers, writers bring in the retcons to tie up all the loose ends.
Retcons are a cheap and easy way to explain away any discrepancies in a character's storyline, and few superheroes have had their story retconned as much as our feral pal Wolverine.
Wolverine was initially referred to as Weapon X, then Weapon X became the name of the whole super-soldier program that laced his bones with adamantium and temporarily broke his brain.
A few retcons later the "X" in Weapon X was ultimately revealed to be a Roman numeral, meaning Wolvie was project 10 and even Captain America is considered to be part of the "Weapon Plus" program.
That's some mighty convenient retconning, but not as convenient as Wolverine's healing factor retcon, because at first he took a lot longer to recover from grievous injuries, leaving Logan laid up for weeks.
By the 90s Wolvie's healing factor had gone mega, because according to writers it improved every time he used it, so he was able to recover from being fully incinerated in just a few hours.
But to me the weirdest and most ridiculous retcon of them all is the bit about Sabertooth being Wolverine's father.
Sabertooth became Wolvie's archenemy because they both have a very savage fighting style, but Chris Claremont tried to to serve up a fastball special by having Sabertooth reveal Logan was his son.
In the next issue Nick Fury conducts a DNA test and proves Sabertooth isn't Logan's father, making the whole thing feel like a bad episode of the Maury show! Sabertooth, you are not the father!
See Wolverine's 15 Craziest Retcons here