Despite being the Star Wars universe's greatest arch-baddie, much of Emperor Palpatine's life remains shrouded in mystery. While we've seen Anakin's journey from adorable '90s towhead to his final unmasking, Sheev Palpatine's life seems to begin at middle age. We eventually learn he apprenticed for Darth Plagueis, but all of this is anecdotal. However, a peek into the non-canon elements of Palpatine's life reveals a whole other side: one we could possibly see in future movies.
Much of what we know about pre-Senate Palps comes from the non-canon novel Darth Plagueis by James Luceno. It details the journey of Sheev's fabled master, with a whole lot of murder in keeping with the Sith Rule of Two.
Palpatine's backstory is also detailed in this story. Born into the House of Palpatine, Sheev's father Cosinga was a minor royal of Naboo, but never sought more power. This angered the young Sheev, whose ambitious nature was already shining through.
Much of Palpatine's life was influenced by his father: when Sheev would lash out at school or generally rebel, Cosinga would bribe a flunky to ensure his son got off scot-free. This helps explain Sheev's catty entitlement in the prequels and original trilogy. He grew up knowing that money and power would insulate him from the consequences of his actions, no matter how terrible they are.
Sheev and his dad did have one common passion: speeder racing. Sheev even raced competitively for a while, much to his father's chagrin. This could explain why later, when he rejects his family completely, Palpatine bans podracing: perhaps the thrills remind him too much of his father.
While studying at Theed University in the Naboo capital, Palpatine meets Darth Plagueis in the guise of his public persona, Hego Damask of the Intergalactic Banking Clan, and offers to show him around. As they talk more, Palpatine agrees to be a spy within Naboo society. This is the first step in creating what will eventually become the entire plot of the Star Wars movies.
Darth Plagueis sensed the anger young Palps had for his father and drove a wedge between them. This was brought to a head when Cosinga planned to send Sheev away to finish his studies. Young Palpatine got angry and eventually snapped, slaughtering his entire family and leaving him the last of the House of Palpatine. It was this act that proved him worthy to be a Sith, and Darth Plagueis gave him the name he would then use to lord over the galaxy: Darth Sidious.
That this entire story remains outside official Star Wars canon is a shame. An aristocratic father/son betrayal aboard the family yacht was literally the Season 2 finale of HBO's Succession. Perhaps the future of the Star Wars universe lies in a further prequel, filling in the blanks and answering old questions about the Galaxy's most feared villain.
Exploring the Emperor's younger years could breathe new life into the franchise, providing both a new anti-hero in Palpatine, and a new terrifying Sith Lord in Plagueis, and the same prequel-era dramatic irony in knowing these characters' downfalls, each at the hands of their apprentices.