There are a lot of characters in You Can't Take It With You; the screenplay calls for more than a hundred and fifty parts. Many of these are just faces in a crowd, or folks passing through. With so many characters, there's not space in the film to do much more than give them each a cute characteristic apiece—or at best, a hobby.
Kirby's extremely stressed out real estate agent. You can tell he's extremely stressed out because he has a tic; his face keeps flinching. Grandpa makes fun of him for it, which seems like a pretty mean thing to do. But then, Mr. Blakely isn't very nice either—he did conspire to get Grandpa and everyone arrested, after all. So maybe it all works out.
Essie's husband Ed likes to play the xylophone, print up leaflets, and catch Essie when she jumps into his arms. He often seems a bit confused, but that could happen to anyone living in the Sycamore house.
Alice's sister, Essie, loves dancing (even though she's not especially good at it, according to her cranky Russian dance instructor). But Grandpa doesn't mind as long as she's happy. And Essie does seem pretty carefree.
Donald is Rheba's fianceé, and he does odd jobs around the Sycamore house. He's also receiving relief, or unemployment; that was very common for people during the Depression. It's not clear whether the Sycamores are paying Donald for his work; hopefully they are. Otherwise they're kind of jerks.
Mr. DePinna's the iceman, who showed up nine years before the film and stayed to help Mr. Sycamore work on fireworks in the basement. He also dresses up as a discus thrower so Mrs. Sycamore can paint him. As a personality he's not that distinguishable from Mr. Sycamore, but he helpfully adds to the chaos in the Sycamore house.
Wilbur G. Henderson, IRS Agent
The IRS agent is there to sputter while Grandpa looks clever. No wonder he looks so cranky; who wants to let the other guy get all the good lines?
Mrs. Kirby is a big ol' snob who doesn't want her son marrying that awful stenographer. Actress Mary Forbes does a great job throughout the film looking like an unpleasant animal has crawled up her nose.
There's a moment at the very end where Kolenkhov whispers something to her and she starts to laugh and loosen up, though it's not clear what he could possibly have told her to make her happy. Perhaps he said it was all a dream and Tony wasn't marrying Alice after all? Or that he had a surefire cure for getting small animals out of her nose?
Kolenkhov is probably the most entertaining of the funny bit parts. The actor Mischa Auer grimaces and mugs his way through the part, thoroughly enjoying himself as a dour Russian who is filled with joy at the chance to declare that everything stinks. At the time of the film, Russia was deep in the throws of Stalinism, so Kolenkhov is presumably a fugitive—which makes it all the more ironic that he is arrested (along with the rest of the household) for spreading seditious Communist propaganda.
Night Court Judge
Capra is a big fan of democracy and the awesomeness of the United States, so he makes his night court judge a thoroughly friendly guy, who tries to be fair and kind and even tosses in a bit to pay off Grandpa's fine. If you go to court yourself, don't expect the judge to be like this. You will probably be disappointed.
Actor Donald Meek almost always played characters who were—well, meek. Poppins is one of his more famous roles, in which he does his usual thing, stuttering and trembling and generally meek-ing.
Of course, in You Can't Take It With You, Poppins gets to come out of his shell, and embrace his inner tinkerer and prankster by making toy bunnies and scary masks. His story is an early foreshadowing of Kirby, who also by the end of the film gives up his tedious pursuit of money and numbers (though Kirby doesn't make toy bunnies, admittedly. Maybe some day, though.)
Ramsey is the guy who Kirby ruins by buying up all the land around his munitions factory. Ramsey used to be Kirby's friend, but Kirby is so ruthless he doesn't care. So poor Ramsey has a heart attack.
And then Kirby changes his mind, and sells Grandpa's house back to him… which means that Ramsey wasn't so ruined after all, and could have gone on with his business happily. But of course Ramsey can't do that because he's dead.
Not that anyone cares; the film pretty much completely forgets that Ramsey exists, and paddles on with Mr. Kirby cheerfully playing the harmonica. You'd think Kirby would feel guilty, but that would put a shadow over the happy ending, so Capra just forgets about it. Sometimes you need to kill a couple of business rivals to find your inner harmonica player. That's the way it goes.
(Disclaimer: Shmoop does not condone the accidental murder of business rivals in the pursuit of musical goals.)
Rheba doesn't dance or paint or write or build fireworks; she works as a servant.
For the time period, having Rheba (who's black) interact so cheerfully with the family was potentially controversial; racists didn't like it. So in that sense you could see the film as progressive or forward-looking. The fact remains though that in a film devoted to the idea that everyone should follow their bliss, Rheba's bliss is presented as involving setting the table and running errands for someone else's family. It would have been nice if she'd been able to make toy bunnies too.
This is Alice's dad, who seems oddly uninterested in the fact that his daughter is getting married. Sure, he's playing around with his fireworks, but wouldn't you think he'd be a bit more involved?
Of course, the reason he isn't is that the star of the movie is Lionel Barrymore, who plays Grandpa… not Samuel S. Hinds who plays Mr. Sycamore. There's only so much room in a film, and Barrymore takes the role of the concerned family member. So Mr. Sycamore comes off as a pretty callous father figure.
Penelope "Penny" Sycamore
Penelope is Alice's mom, who writes and paints and occasionally picks up an extremely cute kitten. We learn from Alice that Mrs. Sycamore started writing because someone accidentally delivered a typewriter to the house.
She writes by chance, as a casual hobby, not because she's actually committed to it or passionate about it (she is just as happy painting). The Sycamores like the arts—but they seem careful not to like them too much. If Essie were to actually get a job dancing, or Mrs. Sycamore were to sell a manuscript, art would become work.