Omg I love this question. At first I thought WORLD WAR II THINGS, but knowing the Doctor (Tenth), we would probably discover that the Resistance has been infiltrated by Slitheens or something. Besides, there have already been two too many WW2 related plot-lines in the new series. And it wouldn’t be safe.
Then I considered the March on Washington, a Vietnam protest, or the 1968 Democratic National Convention, but then I realized what the true answer must be: the Second (1618) Defenestration of Prague.
I am sorry, but Funniest Historical Event Ever.
(tl;dr for those not familiar with the event: tense discussions between Protestant and Catholic officials ended with the four Catholic officials being thrown out of a window. They landed in a pile of manure. This event hastened the onset of the Thirty Years’ War.)