Character Analysis
What with the way the economy is these days (or back in 1910), Bert's got to hold down three jobs: he's a one-man band, a chimney sweep, and a chalk-sidewalk-drawer-person. He's also someone who has the ability to speak directly to the audience, at least at the very beginning of the movie…and later goes into the kite-selling business. He's a jack-of-all-trades and a master of fun (hey-o!).
Bert hangs out with Mary—who he already knows—and helps watch over the kids after they run away from the bank. He's generally a helpful, likeable character with a cockney accent. (Linguistic mini-lesson: cockney is a dialect commonly heard in London. For instance, the actor Michael Caine has a cockney accent). He's got a little less social status than the kids' back manager dad, but he's got the kind of personality Mr. Banks needs to learn to have.
Bert isn't just a fun guy to be around. He's also a useful guide, explaining things, both to the audience and the kids. When the kids complain about the way they're treated, Bert tells them:
BERT: Let's sit down. You know, begging your pardon, but the one my heart goes out to is your father. There he is, in that cold heartless bank day after day, hammed in by mounds of cold heartless money. I don't like to see any living thing caged up.
Bert sees things clearly: he recognizes that the central conflict of the movie is taking place inside Mr. Banks. And he's helping Jane and Michael understand this. They need to help their father to change, because he's the one who's actually suffering the most. The story isn't just about them.
But Bert exists primarily to entertain. He goes on an extended singing and dancing binge with Mary, when they enter the animated chalk-drawing world. It even seems to be a kind of…date. Yet, Bert is what you'd call a perfect gentleman, and it's hard to figure out if he's really trying to wife Mary up. At one point Mary sings:
MARY: You'd never think of pressing your advantage / Forbearance is the hallmark of your creed.
So, Bert isn't making any brash moves. He likes to take it slow—if he truly is Mary's boyfriend or whatever.
Bert also participates in their adventures with Uncle Albert, and with the chimney sweeps who sing and dance to "Step in Time." He's a cool guy to be around—even if his nature is shrouded in mystery. Where does Bert come from? (Well, London, based on his accent). How come he's so unfazed by Mary's magic? How did he first meet Mary?
It's possible we'll never know.
Bert's Timeline