Hmm
Spoiler: show
I guess it would make sense if the Observers were something akin to the Shapeshifters, but instead of cyborgs from the alternate dimension they're cyborgs from the future. Maybe it was Peter who created the Observers in the future and the doomsday machine, and sent them both back in time to aid present Peter. That would explain why the Observer saved the last copy of Peter from drowning under the ice (to avoid a paradox), and why the machine only responds to Peter's DNA.
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