Loki is in a cell on Asgard, paying for his crimes. You appear in his cell one night and offer him a chance to go back in time and make different decisions. The option is here in case you'd like to make it NSFW ;)

DW. The 10th regeneration of Doctor Who. From a planet called Gallifrey. Also making him dominant just because ;)

You're a best-selling author. The third and final installment of your Epic Fantasy Series was recently released, and prior to that you held a first chapter reading which Bucky went to because he loves your books. You hung out a few times and got to know each other, and he confessed that he wanted to walk away from fighting for a while, so you offered him a safe haven at your place while he figured out what he wanted to do. He moved into your spare room yesterday. How will it go? Have fun! ;)

You have certain Empathetic abilities, and a dangerous mob had captured you to force you to use them for their gain. You try and escape, only to end up transporting yourself to the safest place in the Universe — the TARDIS. *Set in season four, not long after Donna left. *SFW intro with the possibility of NSFW themes (whatever you choose). *Haven't specified the POV so hopefully its suitable for anyone. *Personally, I'm going with the soulmate trope which will be fun ;)