The Greek Gods were actually ancient aliens
Mark Twain went through a time portal and hung out on the Enterprise-D
Amelia Earhart was abducted in 1937 by aliens and put into cryostasis until the year 2371
The Roswell Incident really happened it was the Ferengis from Deep Space Nine accidentally caught in a time warp
Vulcans crash landed in Pennsylvania in the 1950s and introduced the concept of Velcro to humanity
All modern computing was invented because the technology was reverse engineered from a 29th century timeship that crashed in California in 1967
A Romulan secret agent sent back in time to impede human progress implied that the JFK assassination and Chernobyl were alien attacks designed to impede human progress*
*(she did this undercover as a human conspiracy theorist before her true form was revealed)
Methuselah, King Solomon, Alexander The Great, Lazarus, The Wizard Merlin, Leonardo Da Vinci, and Brahms were all the same ancient immortal guy who moved to space when the Federation was founded to become a rich space capitalist and lives alone on a planet he bought and spent years working on building the perfect robot wife until Kirk made Version 17 of the wife so horny that she died.
I am forever in awe of how - in order to protect the timeline - Vulcans were responsible for the Apollo 1 fire.