Hahahaha Age Swapping! I'd also vote superpowers but only if Marcus gets a lame one. Like he's the Wonder Twin who turns into water or something. Because if he had a good one his ego would be difficult to deal with. Now I'm just combining ideas. Marcus wakes up one day with the dubious superpower of being able to turn into a teenaged girl. And they're all in a space western.
(Random Geek Fun fact: Star Trek was originally conceived and pitched by Roddenberry as Wagon Train in Space.)