Harpo Marx guest-stars on I Love Lucy. There's so much goodness in this one clip, it's ridiculous. Not only do you get Harpo and Lucy doing the mirror sequence, a call-back to Duck Soup, but you also get Ricky and Fred as the other Marx Brothers. See? Ridiculous. And I have trouble enough just moving myself, much less doing a choreographed mirror sequence with somebody else. In front of an audience. That must have taken freaking forever to get down.
If I've got it right, this was from Season 4 and should be on this DVD.
And of course, the original bit from Duck Soup after the break.