Maybe Ingo wasn't just sent back in time, but to an alternate dimension. Then when he gets 'home' it's just thst place's future, not his original dimension. The Ingo here was never ebby deebied so now there's two Ingos.
Then the Emmet who lost his brother tracks him down somehow and there's four train twins lol.
thats kind of what i think happened tbh? assuming it was in fact a wormhole, thatd have to be how it is. ingo just entirely out of place... and a very panicked emmet















