Impossible Mission Collapse

A gag where an elaborate, high-risk plan is concocted by the good guys, we hear all the planning, and then it never gets past step one. There are three varieties:


 * 1) Instant failure. eg, Once they all know what they're supposed to do, they step out the door and immediately one of them trips over and breaks a leg. This never occurs in shows where the heroes are professionals.
 * 2) Instant discouragement. eg, Once they all know what they're supposed to do, they open the door, notice it's raining and call the whole thing off. This absolutely never occurs in shows where the heroes are professionals. For an example, see the movie Pluto Nash where some professional singer explains to Eddie Murphy how to get to the bad guy's penthouse... and Murphy asks if there's a plan B.
 * 3) Instant success. eg, The convoluted scheme for breaking into the bad guy's vault becomes redundant when they get there and find the door has been left ajar. This is particularly effective when the instant success is achieved by good old common sense, such as the scene in The Bourne Identity where Matt Damon coaches Franka Potente in how to obtain information from a hotel clerk, and she succeeds just by asking for it. (Compare Cutting the Knot.)

Sometimes this joke gives itself away by having the plan be too elaborate, too dicey, and explained in too much detail.

Subtrope/converse of the Unspoken Plan Guarantee.

Film
"Stef:What about the Fratellis? Andy:Yeah, those creeps are still after us! Mikey:I've got an idea. I saw this on an old Hardy Boys episode. We'll leave a trail of jewels leading into one cave while we hide out in another. When they go into that cave, we'll make a run for it. Mama Fratelli:Now, that sounds like a great idea!"
 * In The Bourne Identity, Jason Bourne creates an extremely complicated plan to retrieve a phone bill for a hotel room he stayed in. It includes sending Marie into the hotel's lobby, counting how many steps she takes, making a total head count of all the people in the lobby, and looking out for security. He asks her if she remembers the number and locations of all the exits and all the signs she has to give him if she think she has been spotted and is being followed. Once she's inside the hotel, he will make a call on a pay phone to the phone in the lobby for her to pick up. And that's just the very first step of the plan to spy out the place. She goes inside and Jason calls the phone, but gets increasingly nervous when nobody is picking up. Which is because she's already standing right next to him with the phone bill in her hand, as she decided to just ask the clerk at the desk and he gave it to her.
 * The bet in the last part of Four Rooms. It's over less then a second after it started.
 * The remake of The Italian Job has the crew go over a complex plan to steal their gold back from Steve. When they go to implement said plan, they discover Steve's neighbors are holding a party. They call off the heist due to the large number of witnesses.
 * The Goonies features possibly the fastest Type 1 example:

Literature

 * The trio's plan to break into the Ministry of Magic in Harry Potter and the Deathly Hallows. Professional in the planning, not so much in the execution (mostly due to the fact that none of them works all that well under pressure). They ended up improvising everything on the fly instead.
 * Actually, they only ever planned on how to get in and seemed to think everything else would work itself out because that's how it's been in the past.
 * Lampshaded by Harry wondering why they didn't plan anything for after when they get in.
 * In The Dresden Files novel Changes, Harry Dresden and his comrades prepare a careful plan to launch a distracting attack on the Red Court's holy site at Chichen Itza, while Harry himself and a small group sneak around and rescue  from the vampires. They set up the entire plan, get ready to move out - and then a human prisoner of the Red Court stumbles into the clearing, being chased by a vampire who is quite surprised to find the group. The vampire lets out a scream of warning before being killed, the entire Red Court army is alerted, and the team has to go to Plan B.

Live-Action TV

 * The Firefly episode "Ariel", in which the crew are sneaking into a hospital and have a long speech memorized using all kinds of medical jargon. They are allowed into the hospital without having to provide an explanation, but Jayne feels the need to make the speech anyway (and gets it wrong to boot).
 * Even more so in the episode "Shindig". Mal is basically under house arrest pending his big swordfight with Atherton Wing; back on Serenity, Badger and his men show up to lock down the rest of the crew and keep them from doing anything disruptive (that could harm Badger's "standing in the community"). The crew spend most of the rest of the episode cooking up an elaborate plan to distract and overpower Badger and his men in order to ride off and rescue Mal. They're just about to swing into action...when Mal shows up, having successfully gotten out of the situation on his own.
 * The Buffy episode "This Year's Girl" begins with Buffy planning an elaborate scheme to break Riley out of the Initiative. She's still explaining her plan when Riley shows up, having left with permission.

Western Animation

 * Dexter's Laboratory. This happens to Dexter after Dee Dee has him running around for an entire episode to find an item of his. He devises an elaborate plot to hide one of her own items, but she just searches her room and immediately finds it.

Real Life / Truth in Television

 * There is a fairly popular military saying that states that "no plan survives contact with the enemy", encouraging to keep plans simple. Complex plans are easily foiled by the enemy doing something unexpected.