This one is an easy one because I’ve already done it, though in this case I did it with 3 games, rather than 2.
I ran a game that combined The Strange, Numenera and A Penny For My Thoughts. Sadly it’s sort of fallen apart like most of my online games tend to do and I don’t really feel like resurrecting it, but it was an interesting experiment.
The basic premise was that the players were all agents of The Estate. They were on a mission to explore an artificial recursion created as part of an experiment being run by The Estate. The experiment was one in measuring the effects of active engagement with the fiction that was used to seed a recursion - would it accelerate the recursions growth and maturity? Would it have any effect at all? In this case, Researchers Cook and Germain, under the supervision of Chief Researcher Cordell, created a line of roleplaying games called Numenera, and created a recursion based on the game setting. As with all new recursions, it was very basic, small and limited, so after a few months of the roleplaying game being in general circulation (and it being quite popular to boot - a nice hidden income for the Estate to use!) they decided to send in a team of trained Agents to explore the recursion and report back on it’s growth, if any.
The game started out with the players as amnesiacs in some strange, dilapidated facility. They were forced through some kind of chemically assisted group therapy session to regain their memories (A Penny for My Thoughts). Because the game started out this way, they knew nothing of Earth, The Strange or that they’d been sent on a mission - it was just a curious beginning to what seemed to be a normal Numenera adventure (but with characters that had Types from The Strange). Development of their backgrounds and personalities happened via A Penny for My Thoughts, then they managed to escape and discover that they weren’t playing their characters at all - they were playing clones of themselves, hence the memory loss. Clearly they’d stumbled into some ancient cloning facility whilst exploring and become trapped and cloned.
The game was a lot of fun, they found their original selves (some managed to awaken them, some failed or even killed them by accident) and the backgrounds they came up with together made them all out to be fairly nuts (I probably should have set some expectations for the memory part of the game, but meh, it made for fun, if silly, characters).