Character Analysis
Mary Poppins has an uncle, Albert. Who knew? We assumed that she was some sort of eternally existing god-being, who helped children throughout the ages. But, apparently, she's got an uncle.
Uncle Albert loves to laugh. He can't help it. And it also makes him float in the air (like in Willy Wonka and the Chocolate Factory, except that was with soda). Mary, the kids, and Bert have to help him get down, but he keeps telling horrible jokes, which hold him aloft. Eventually, the kids and Bert start laughing and they float too.
Mary acts like this is really irritating, yet, in the end, it turns out she can simply yank Albert back down out of the air through magic. But, if she'd done that in the first place, they wouldn't have gotten to the "I Love to Laugh" song. So, she has to wait for her cue.
Albert fits in with the movie's whole theme about lightening up and letting "a spoonful of sugar" help the medicine go down. Life can't be all about discipline and rules. It has to involve the human touch, humor, and kindness.
But, that being said, Albert's jokes are intentionally pretty bad. Not filthy bad—corny and lame bad. Bert gets in on the act as well:
BERT: I know a man with a wooden leg named Smith.
ALBERT: What's the name of his other leg? …Wasn't that funny?! What's the name of his other—
So, you get the idea. These jokes are horrible.