I'll start - a comedic misprint means that everyone in Texas has to vote for Donald Trump or Hoe Biden. As a result, Texas goes blue but its EC votes are wasted.
Biden disappears for several weeks. It's revealed he died of COVID and Dems were trying to figure out a way forward without telling anyone. Trump declares himself winner a month before even early voting started. During his victory speech, Trump dies on stage. His followers rip his body to pieces and consume him on the spot.
During his victory speech, Trump dies on stage.
Take it up a notch - Trump's been dead for six weeks, they've just been Weekend-at-Bernie'sing his dead ass
Funniest possible ending now:
Nevada swings to Trump, Trump wins 274-264, faithless electors swing it to Biden
This is also the only plausible scenario where the Electoral College is ever abolished
My new favourite ahead of Biden winning 270-268 with the slimmest possible amount without having the state delegations to win a tie
Also - Amy Coney Barrett dies (of covid) right before the election and suddenly lib talking points about the Supreme Court seat come right back.