Go back in time and try to flag down Archduke Ferdinand’s motor carriage only for the driver to get freaked out and go down the alternate route right to where Gavrilo was trying to get to the original route but was running late because another time traveler delayed him…
There is an ongoing study showing that artificial sweeteners (Aspartamein particular) cause cancer.
All those people trying to stay healthy to drinking diet things… are giving themselves cancer instead.