My thought was that Clara surviving is already a potential disruption; and/or he knows that Clara (a scifi fan of her day) would keep bugging him to build futuristic stuff. For the woman he loves, sooner or later, she could break down his self control. So better to build the time machine and get back to the time he belongs in, where anything he does can't actually break the future.

Maybe the train is a less-sophisticated time machine anyway, based on the components available… if it can only go forwards, there's no risk of paradox. (though the animated series kind of breaks that theory)

I think this list is more about characters with different backstory and motivations. There's another article (I think by the same author, not sure) listing characters whose powers are different; and the ten rings get a full mention there.

This sounds bad enough to make me glad I've missed out on the latest season of What If.

Wasn't the emerging celestial supposed to consume the life force of everyone on the planet to fuel its birth? I mean, I can kind of buy the hand popping out without geological damage because It's Magic™, and clearly if there's a baby celestial inside the Earth then everything we know about geology is some kind of protective illusion.

But having people survive the awakening just seems like they discarded canon. Unless the Eternals stopped it, but later in this universe, so the planet couldn't stay in one piece without magic? But that still feels more of a stretch than I'd hope for.

Marty asks if it's a Delorean, then a couple of seconds later asks if Doc's outfir is a Devo suit. Doc is so excited about his invention that he talks over him and doesn't answer either question clearly.