The Star Wars franchise spawns more theories than perhaps any other, but Andor has created perhaps one of the most intriguing.
Franchise veteran Sam Witwer showed up for a cameo as a Stormtrooper in the Disney+ series and was the one who wrongly arrested Cassian on Niamos. That resulted in the title character being sent to that horrific Imperial prison where he'd eventually stage a breakout alongside Kino Loy and then realise a future as a Rebel was his destiny.
While that story will continue playing out in Andor season 2, we know how the hero's story ends; in Rogue One: A Star Wars Story, Cassian helps Jyn Erso steal the Death Star plans and eventually makes the ultimate sacrifice to ensure his fellow Rebels can use those to destroy the Empire's greatest weapon (which they do, courtesy of Luke Skywalker, in A New Hope).
As you can see in the Tweets below (via SFFGazette.com), this theory suggests that Witwer's Stormtrooper is the real reason for Cassian eventually becoming a Rebel and helping destroy the Death Star.
We can't really argue with that one!
Witwer has given the theory his seal of approval and, as mentioned, is an actor with plenty of history in this Galaxy Far, Far Away. After playing Starkiller in The Force Unleashed video games, he'd go on to become the voice of Darth Maul, portraying the villain in The Clone Wars, Star Wars Rebels, and Solo: A Star Wars Story.
He's even played Emperor Palpatine when Ian McDiarmid has been unable to do so, but his unnamed Stormtrooper may well be the most important addition to the entire franchise based on this theory...