You remember when Kari said she could "totally handle anything this baby could dish out"? Well, in this short, she puts her money where her mouth is.
The short begins with Kari being interrogated by Rick Dicker. She begins to recount her recent job babysitting 'Jack-Jack' Parr, and the film flashes back to her reassuring Helen Parr that she can handle Jack-Jack. The phone call cuts off (because Syndrome had just attacked Helen's plane, but Kari doesn't know that). She gives Jack-Jack some toys, and puts on a Mozart CD. She then turns around - and Jack-Jack's gone. She looks around for him, and finds him behind a flower vase on the dining room table.
She thinks he's playing hide and seek, and runs up and takes away the vase - but he's not behind it. He's at the refrigerator, getting his bottle of milk. She comments on how weird that was, and tells Jack-Jack to wait there while she calls Helen (the first of the calls from her that Helen gets when she's going home after defeating the Omnidroid). Jack-Jack doesn't teleport any more, but he does float up to the ceiling. When she turns back around, she freaks out upon seeing him gone. While she looks for him, Jack-Jack pulls the lid off his milk bottle. She's right under him, so she gets splashed with the milk.
This is the least of what she's going to get put through. Later that night, she's put Jack-Jack in a playpen (with a chair on top of it to prevent him from getting out) and she calls Helen once more. During the call, she glances away for a bit - and when she's glanced back, Jack-Jack has chewed his way out of the pen. She notices him on a shelf, and rushes to catch him as he falls over - but he phases through her hands and the floor. She frantically searches for him as he floats through the house, phasing through the walls, and eventually manages to catch him when he's in the middle of phasing through the washing machine door.
Kari then decides to calm Jack-Jack down by playing with flashcards. Unfortunately, her third card, 'Campfire', gives Jack-Jack ideas. He bursts into flames and runs around the house, leaving little fires wherever he steps. Kari chases him with fireplace tools, and eventually puts him out by dunking him in the bathtub.
By the next day, Kari is exhausted, but she's gotten used to Jack-Jack and can counter whatever powers he comes up with. Sets himself on fire again? She's got a fire extinguisher at the ready. Points Eye Beams at her? She holds up a mirror and deflects it up to the ceiling. She hears a knock on the door and goes out to answer it. Syndrome is at the door.
Kari: Yes! I'm Kari, the baby-sitter!
Syndrome: (unnerved) Well, hello... uh, Kari. I'm-
Kari: *Holding out Jack-Jack* You're my replacement, THANK HEAVENS YOU'VE COME! What does the 'S' stand for?
Syndrome: For... 'sitter'! Yeah, sitter. Originally, I was going to have initials for 'baby-sitter', but then I would've been going around wearing a big 'BS', and you understand why I couldn't go with that.
Back at the interrogation room:
Kari: The baby was EXPLODING! YOU EVER SAT AN EXPLODING BABY BEFORE, MR. DICKER?
Dicker asks if she told anyone else, and Kari reveals that she told her parents, but they didn't believe her. Kari comments that she wishes she could forget the whole thing.
