What’s the best prank in uniform you've seen? Comment below!

I was usually against "pranks" but while I was in a stealth program I sent a new troop to get the aircraft forms from one of our "assets". He came back telling me the hangar was empty.
I immediately did a face palm and told him the "stealth" switch must still be "on". I explained to him that he would have to go back, proceed carefully and find the wing then feel his way forward until he got to the crew ladder then get up to the cockpit and find the the "stealth" toggle switch on the left console. I told him it was larger than the other switches so it could be found under these circumstances as it had happened before.
He dutifully left and 4 or 5 of the techs and myself ran out to the back of that hangar. There were gaps in the hangar doors so we could see inside. He came in and moved slowly forward with his arms extended in front of him. We tried to suppress laughter until we were in tears, especially when he realized the hangar was empty and cursed in imaginative ways. My ribs hurt from laughing and had tears streaming down my face as did the other techs.

1975 - I was assigned to the 385th Signal Company at Fort Gordon, GA. Fort Gordon is also where The Signal Corps trained their Lieutenants. During their Lieutenant training, they were sent to the field for one week to learn the equipment, hands on. I was a SP5 in those days, and all SP5s were smart alecks. We had TT-76 teletype machines that made or read the paper tapes to send teletype faster than a human could type. We did this prank every time we had to support the Lieutenant training classes. We would ask the second lieutenant to dump the chad bucket out at shift change. Chads are the little dots punched out from the paper tape. The lieutenant would dutifully dump the Chad bucket in the trash, and then we would all stare at him in shock. He would always then say, “what, what, what?” We would then tell him that he didn’t run the bucket through the Chad counter. These chads were classified, and every one of them had to be accounted for. Now he would have to count them by hand, we usually let him get up to near 1,000 before we gave him the break.

During my time overseas it was SOP to be sent out to a carrier group on deployment in 90-day deployments. Needless to say, there can be a certain amount of personnel turnover while you are deployed. I had just returned from a deployment of 115 days and was just coming off crew's rest when my LPO handed me my first assignment as a CDI and I headed out to one of our birds to oversee the job. Now at the time, we were working under summer work uniform regs which allowed for removal of the dungaree shirt and thus rank insignia on the flight line. I walked up to our bird and stuck my head inside to introduce myself as the CDI for the job. Before I could speak one of our newly transferred PO2s turned to me and thinking I was a newbie, since he did not recognize me, told me it was about time I had gotten there and they were going to need a wire stretcher to make the installation of new wire bundles work right.
One of his crew knew me and was about to inform him of his error but I waved him off since his attitude had annoyed me. I just nodded and headed back to the barn to let the maintenance Chief in on what was going on. (BTW I had just passed my 24-month mark on the base and was extended for another 18 since we always needed experienced people.).
I asked the chief when we needed the bird and was informed that the job we were engaged in was presently low pressure because Powerplants had a phased inspection in work and would be working on that for at least 2 days. I gave him an evil smile and informed him of my plan which earned me a laugh and a nod to proceed.
I checked out a tractor and headed over to visit the Seabees camp.
Now about 4 months earlier the Seabees had gotten tasked with running new razor wire on the base perimeter and had been tearing through gloves like no one's business. One of them who used to be part of my gaming group had gotten himself a commendation for coming up with a solution. They had rigged up a trailer that played out the wire evenly and was fairly easy to load with new rolls. Now enter me with one of our small tractors and ask after my friend. In fairly short order he introduced me to his chief and we explained the situation and my request to borrow their "Wire Stretcher".
Fortunately, my chief was known to his chief and I was soon handed the paperwork to loan the apparatus to our squadron. The Seabee chief did make the requirement that since it was our erstwhile new PO2 who had "requested" the equipment he would like for him to explain to him personally the inventive inspiration for the use he wanted to put their equipment to in solving our problem.
About 20 minutes later I drove my prize out onto the flight line and parked it at the nose of our bird and stuck my head inside and handed my would-be comedian the paperwork for the wire stretcher and passed along the Seabee's wish to consult with him on his use of their equipment. stepped out and unhooked the trailer and returned the tractor to the line shack. I then went back to the shop, put on my shirt, and went back out to reintroduce the team leader to his CDI for his task.
It took him a while to live that down to the point where the Maintenance Officer and Chief would ask him as he headed through the office if he had any new inspirations to offer.

Bag of A-I-R

10 feet of gigline

Fetching a prick e-eight

Zip tying the zippers on the coveralls

Send newbes to get keys to locking bars on a NikeHerc launcher elevator. Was always interesting to hear what maintenance folks told them.

Not in military but a similar situation. I worked on the Alaskan Pipeline after I left active duty and completed grad school. Some of the pipe fitters I worked with told of a couple of Cajun Pipe Fitters that had a new apprentice. They sent him on the usual run of useless tasks. One day they were trying to complete fitting up some pipe and found needing a "plumb bob". Told the apprentice to go to the tool rook and ask for said device. Apprentice said, "I'm not going after. No one has ever heard of a "plumb bob."

Mail bouy lookout was a common prank. On subs, we used to have the non-quals look for the screen door.

Snow snakes in ND. FNG took the tall tale that I told WAYYY to serious, belly flopped on to the hood of our patrol truck when I yelled his name, snake, jump! Though it was funny as hell. Welcome to the AF SP's.

At Myrtle Beach AFB the new guy in fuels was always sent out to the end of the taxiway to wait for the arrival of the GU ll. After about 15 minutes on the radio saying 'it's not here' and the dispatcher saying 'I can see it from here', it finally dawned on the new refueler that the GU ll was really a gull like in seagull.

The Lieutenants in my Battalion would call the orderly room of another company, identify themselves as the Battalion Commanders assistant, and state the Battalion CDR wanted to see Lieutenant "X" in his office. The message would be passed, Lieutenant "X" would go to BN HQ, knock on the BN CDRs door, and state "Sir, you wanted to see me?" BN CDR would state "No...why would I want to see you?" An interesting sequence of events...