I dub this episode
12 Monkeys for Algernon Five.
It's a little disorienting (ha ha) to see the show dip into several very familiar SF tropes that don't really appear elsewhere. It's kind of interesting how they're all so tightly bound to just this one character.
Seriously tho
Agreed that it was a great one-off. I was gonna comment that it didn't feel very "Losty" because it replaced flashbacks with time travel (which aren't the same at all). But then I remembered that they did this (or something almost like it) with this character before.