Elevator Buttons Mash

Ah! Sorry it took so long. Someone accidentally hit all the buttons in the elevator on the way up here. [Beat] It wasn't me.

—Ruby, RWBY

A person in an elevator car pushes buttons for several or all the floors. Among the reasons:

It may be a kid on an elevator who hits all the elevator buttons as a prank. The buttons light up when pressed so other patrons know they don't have to press them again and the kid wants to light them all up.
The person may be trying to get the elevator to move. This might happen outside the elevator, when the person pushes both the "up" and "down" buttons despite only wishing to go in one direction or the other. Generally signals impatience on the part of the person, a breakdown of the machinery, or both.
The person has a specific reason for making the car stop on multiple floors. Perhaps they're fleeing pursuer(s) and want to slow them down. Perhaps it's a Dying Clue.

Examples of Elevator Buttons Mash include:

Film

Seen in Lara Croft: Tomb Raider - The Cradle of Life.
When an elevator stalls in You've Got Mail a person hits all of the buttons in a vain attempt to get the thing to go somewhere.
In the Doctor Who story Paradise Towers, set in an enormously tall apartment building, the Kangs do this, and the protagonists get stuck in an elevator they've done it to while fleeing from the monsters.
Elf: Buddy presses all the buttons to make them light up like a Christmas tree, then exits at his floor leaving the other elevator users to stop at every floor.
Kung Fu: the Legend Continues: two flowergirls do it at the hotel where a wedding reception is being held. When they stop at a floor that's under renovation Peter sees an AK-47 being held by a Janitor Impersonation Infiltration guy who kept his back to the elevator (Peter seeing the reflection in some brightly polished marble tiles) leading to the plot of the episode.
Happens in Serendipity, as one of the Contrived Coincidences that keep the leads apart.
In A Series of Unfortunate Events, the children do this when they're in the Hotel Denouement, and they're trying to slow down the antagonists. Their father taught them to do it.
Happens to Wolf and Twitchy in Hoodwinked Too.

In Jennifer, Hecate, Macbeth, William McKinley and Me, Elizabeth, the main character does this to her nemesis Cynthia whenever they're in the elevator together.

In an episode of Ellery Queen (the TV version), a dying man pushes certain buttons in an elevator to indicate the office number of his killer.
In one episode of Leverage, Nate does this from outside the elevator- his team are on the top floor, and Sterling is taking the lift up. To slow him down, Nate takes the stairs and runs to hit the Call button on the elevator on every floor.
In the Charmed episode "I've Got You Under My Skin, as Prue is hurrying to make it to her interview at Buckland auction house, and telekinetically makes it happen. Though it turns out one of the other passengers was the person she was supposed to meet with.

In Robert Rankin's The Hollow Chocolate Bunnies of the Apocalypse, Jack is tempted to do this, having never been in an elevator before, but Eddie scolds him not to... but not before he's pushed one button for a floor he didn't mean to get off on.
Angelica does this in a Rugrats episode when her mom takes her to work.

Happens off-screen during V2E8 of RWBY, perpetrated by some unknown person if we are to trust Ruby's Suspiciously Specific Denial.