Singin' in the Rain had some insane dance numbers. My favorite was 'Good Mornin'.'
Which Family Guy spoofed.
The 'Make 'Em Laugh' number was so physically demanding that Donald O'Connor had to take a few days of bed rest after filming it.
And, fun fact, The Comedy Cellar in NYC (which you might know from Louie) —
plays the "Make 'Em Laugh" sequence right before the show stars each night.