Bear Trap Bed

Ah, The Bed. A place of security, stability and relaxation where one can sleep your cares awa.. SNAP! The bed folds in half like a taco shell, trapping the occupant between the raised head and foot. Chances are, if the occupant survives at all, it's a comedy.

A Sub-Trope of Murphy's Bed. See also Bear Trap.

Examples of Bear Trap Bed include:

Pure Comedy

Film

Nordberg in The Naked Gun movies, with his hospital bed.
In Jacques Tati's classic M. Hulot's Holiday, this is done with a rowboat. Hulot's attempts to extricate himself lead to terrified beachgoers mistaking said craft for a man-eating shark.
Q occasionally tests one of these in his lab, often hurting some poor peon.
In the film The Wrong Guys, Richard Lewis attempts to set up a cot in a tent which keeps doing this to him. Eventually he ties this "cot from hell" in place, and is finally able to lie down on it. However, then another character actually causes the entire tent to collapse, and we can see the shape of the cot folding up again underneath it, while Richard screams in agony.

Literature

Mightily Oates's camp bed in the Discworld novel Carpe Jugulum.

Live-Action TV

Crank Yankers featured this in a segment.
Granny from Beverly Hillbillies gets trapped in at least two beds in one episode

Western Animation

Often happens in cartoony hospitals, where someone in a full body cast will have the misfortune of having a bed that will painfully sandwich them. Showed up in Tom and Jerry, Looney Tunes, Popeye and Quack Pack, among others.
In one cartoon, Donald Duck is eaten by a folding camp cot like this.
In Rugrats, Butt Monkey Chuckie gets trapped in one of these.
In The Wuzzles, Croc, seeking shelter from a tropical fruit storm (yes, as in a storm where it rains bizarre hybrids of tropical fruits, like coconut/bananas) by pretending to be injured on a "broken" step (which he himself broke) at Butterbear's, is tossed into bed by a Bumblelion who secretly witnessed his plan. The bed promptly folded up on him (Croc, not Bumblelion).
Parodied in The Simpsons: Homer refuses to get out of bed, so Marge folds it up. We hear a crunch and see red fluid drip out. Terrified, Marge quickly unfolds it, and out tumbles Homer, perfectly fine, but crying over his crushed and dripping juicebox.
Phineas and Ferb. "Flop Starz" Doofenshmirtz falls from the top of a giant robot, only to land into the safety of a nearby bed, which then folds up on him. Talk about insult to injury.
An early episode of The Jetsons showed George's bed folding up lengthwise to turn into a toaster, which then pops him out with all the vigor you expect of a six-foot-long toaster.

Real Life

One spring-loaded canvas-on-a-metal-frame folding thing is generally used as a sun lounger. If you don't set it at the perfect angle, or if you sit down too hard or someone throws a well-aimed pebble, you are instantly trapped in a canvas sandwich that can't be opened from the inside. Thankfully, the frame only runs around the outside edge, leaving the victim only in danger of an uncomfortable squishing rather than a broken back.
It's even worse when employed in combination with a hot water bottle.

Lethal Examples

Film

In Freddy vs. Jason, Jason knifes up a kid in a rollaway bed, then folds it up—with the kid inside being folded backward.
Doesn't that giant plant that eats Poison Ivy in Batman and Robin look like it might be her bed? That she's that overconfident of her plant-control powers and evil that she'd choose to sleep in a carnivorous plant?

Live-Action TV

On My Name Is Earl, one of the guys on Earl's list, Josh, dies via Bear Trap Bed.
In the TV series St. Elsewhere, Mrs. Hufnagel [a recurring character as a patient] dies as a result of a folding hospital bed folding up on her.
This is the deathtrap in The Wild Wild West episode "The Night of the Deadly Bed", with the slight change that it was a canopy bed and the spikes dropped from above instead of the bed folding. Considering that this was the first episode aired after the pilot, it's hardly a spoiler to mention that the deathtrap didn't work.

Video Games

Not done with a bed but still an example. In Bloody Good Time, you can kill someone sleeping in a deck-chair by doing this to them.

Real Life

A man in St. Petersburg was lounging on an unfolded sofabed after drinking. The next morning he and his wife got into an argument and she kicked the bed in a rage, then stormed out. Unbeknownst to her, the kick released its spring-loaded folding mechanism. It folded up with her husband in it and killed him instantly (strong springs + inertia + leverage + being extremely unlucky = broken spine). A few hours later she returned to continue and found him like this.