Doomed timelines

Doomed timelines are a phenomenon in Sburb based on the fact that many events are the result of closed time loops. A doomed timeline is created when a person fails to do what they are supposed to do resulting in a "cascade of misfortune throughout paradox space" causing the entire timeline and it's inhabitants to be doomed. Interaction between doomed timelines and other universes is prevented, however a person can travel back in time from the doomed timeline and avert the timeline ever being created. In fact this is necessary to succeed, meaning a doomed timeline has to exist in order to ensure it's own non-existence.

Kids' session
There have been at least 3 doomed timelines in the Kids' session, the most important being when John under the guidance of Terezi prematurely met Typheus. This would have various effects such the most obvious: John no longer being able to preform the Ectobiology needed to create him, his friends and their guardians or allow Jade entry into the Incipisphere which would mean Becquerel would not be prototyped meaning Jack Noir would not become a threat to the trolls which would lead to their trolling of the kids including the actions which resulted in John's premature meeting with Typheus.