Retcons That (You Think) Worked

[Agent Z]

Norman being behind the Clone Saga. Probably the best way to handle that story after it went off the rails.

[Chainsaw Vigilante]

Apocalypse being the Celestial's practical slave always worked for me.

Apocalypse has an insanely convoluted history that consistently contradicts itself. it's a continuity and retcon nightmare.

-Way back in Louise Simonson's X-Factor run there was this mutant that could control molecules and basically threatened to use her power on Ship (the Celestial ship that
-X-Factor used as a base and Apocalypse did before them), Ship then freaked out and said that that's how Apocalypse enslaved him (him being Ship). So the first piece of continuity was that Apocalypse stole and used his powers to take control of the Celestial ship.
-Then came the Claremont/Lee/Portacio run where this giant Apocalypse called Apocalypse Prime (I'm assuming meaning all the other appearences of Apocalypse was some sort of avatar?) was shoring up power to slay the Celestials (among others).
-Then we had the Rise of the Apocalypse mini where it was established that Apocalypse had his shape changing powers and all the rest from birth.
-After that was the Askani' Son and Cyclops and Phoenix series where an alternate future Apocalypse was some sort of energy being that needed hosts to interact with the physical world because he was too powerful for a body to contain him for long (much like Proteus before him).
-Due to the Askani minis some writers started to use this alternate reality version of Apocalypse as what the mainstream reality one was like, which brought the whole host body crap into the mainstream continuity with the 12 saga but had the Apocalypse form we new of as a suit to contain his host body (you know despite previous continuity making that impossible). In that mini he again was shoring up power to re-write reality and kill off the Celestials.
-Then years later the whole terrible Blood of Apocalypse arc which ended with the Celestials essentially kidnapping a weakened Apocalypse (a plot thread that was never resolved).
-Years later again we got Remender ignoring the end of the Blood of Apocalypse arc, having Nur Apocalypse being dead somehow, and now Apocalypse was essentially some sort of force that was granted a host through a somewhat complex form of succession by the Celestials, basically being a tool they used to further evolution. So Apocalypse somehow worked with/for the Celestials, but AoA Apocalypse slew a Celestial gardener, and so was an enemy of them.
-Following that we had the return to the Age of Apocalypse saga where it was revealed that the Celestials created a race of entities called the Exterminators to use as a force of destruction to weed out things that will prevent the evolution of the multiverse, but the Exterminators rebelled but were too powerful for the Celestials so they trapped them in the space between realities. After that the Celestials discovered some sort of force that was the Apocalypse force that they used as an exterminators replacement to help the multiverse's evolution, but this force wasn't as chaotic as the Exterminators and would take hosts that could be guided. Then the Exterminators were accidentally freed, killed the Dreaming Celestial by draining its' life force and threatened to erase the multiverse and kill off the Celestials, but the Apocalypse force took over AoA Jean Grey, showed some sort of sentience by speaking to her, and she singlehandedly took on and was defeating the entire race of the Exterminators before the AoA reality was sealed off from the rest of the multiverse. The Apocalypse force works in the 616 (now prime) reality through the force is supposed to have some multiversal workings and AoA Jean Grey was sealed off while taking on a multiversal force.
-There was also that Black Vortex saga where the Godhead Celestial looked exactly like Apocalypse (same lips, an A on his belt and all), what that means I do not know.
-In the alternate future that was X-Factor Forever (by Louise Simonson, Apocalypse's creator), Apocalypse opposed the Celestials for humanity.

Yeah so it's weird and continuity constantly undermines itself and is not clear. The closest he was to a sort of slave/underling was in Blood of the Apocalypse, in other stories he was an opponent, worked for them as a sort of tool for evolution, mainly used/enslaved their technology for his own purposes, was a force they merely discovered, etc. I have my own theory that would actually tie things together and leave En Sabah Nur as the centerpiece like he should be, but that's just me.

[Wiccan]

Yep, that was always one of my favorites too. I was a big fan of the O5/X-factor and getting her back was mandatory.

Yeah, sure. There totally wasn't any other way to bring her back but to try and erase all her appearances on an entire run lol.

[super curry max]

Gambit rounding up the mauraders

[K7P5V]

Ultron's personality and memory engrams were based upon his creator, Hank Pym.

Galactus altering the Silver Surfer's mind in order to suppress his guilt of finding suitable planets for his master to feed on.