The Disguise Kit, also known as the Spytron 3000 Disguise Kit, is the default PDA weapon for the Spy. It is an ordinary cigarette case that, in addition to six normal cigarettes, contains hidden and special spy tech. This weapon can make a spy look like any enemy team member of any class, and match their speed if they are slower, but not if faster. This does not change the actual hitbox of a spy, letting a bodyshot of a spy disguised as a heavy likely miss. Also, when disguised, a spy can not pass through enemy team members, or buildings. If a spy disguises as a class that isn't being used, a random name will appear for the class. Disguising takes about 3 seconds, and team-colored smoke comes from the spy as this happens. The smoke is invisible when cloaked, but is still visible if you disguise and quickly cloak. When disguised, a spy will appear to have a mask with the head of the disguised class. If a spy disguises as a spy, a random face-mask will be chosen. This mask is uncontrollable. Due to this existing, Spychecking is common on most servers.
All disguises have pros and cons. Some disguises rarely fool a enemy while moving, such as the Scout disguise. However, it is good for a quick glance and hiding when out of cloak.
These classes are good disguises for the front lines and usually good to get a enemy Medic to heal you.
Fooling chance: low, medium if not moving
Medic buddy? No
The scout has a small body that is good for hiding, but you will not gain the double-jump or speed of a scout, making it a bad disguise while moving. However, it is good for quick glances and is easier to sneak up to a enemy due to it's small size. If out of cloak, this disguise excels at hiding, as the scattergun is good for being short and fat (while crouching), and the bat is good for thin and tall, (Standing).
Fooling chance: medium, medium-high while moving, medium-low if holding the Flamethrower
Medic buddy? Probably, if called for
The pyro has 100% speed, making it a easy class to chase down enemies. But, this may not work as many spies disguise as this class and pyros are generally expected to spy-check members, you cannot fake this. It's flamethrower is very visable since it sticks out a lot. This disguise is good for moving but not for glances. This disguise gives a spy a reason to patrol a base or a spawn.
Fooling chance:high while moving, medium-high if still for too long
Medic buddy? Almost always yes at first
The soldier is a rare disguise, due to the slow speed, since you will not be able to catch up to backstab someone. But, the soldier is a common medic buddy, and if called, the medic will likely heal you at first, at least until you get full overheal. This disguise is fairly good for fooling enemies. Also, this class is a prime suspect as a spy if they aren't moving usually.
Defense These classes give a spy a large reason to stay in a base. However, most of them have a slower speed than 100%.
Fooling chance: high, extremely high if being healed by a medic
Medic buddy? Yes almost always
The heavy disguise is a rare one, due to it having the slowest speed in the game, making it a poor choice for chasing down targets to backstab. Ironicly, because of it's rarity, most players won't expect this disguise, letting you walk fairly easily without being spy checked, especially in a battle. In some maps, like 2fort, de-cloaking and pretending to walk out of the spawn often lets you backstab the snipers on the balcony.
Fooling chance: medium if near enemy stickybombs and moving, low if still for too long
Medic buddy? Only long enough to be topped up to full overheal usually
The demoman disguise is a average disguise in almost all ways, as it has a fairly small body,7% slower speed, and has a reason to stay in the enemy base. This disguise is generally more effective if near enemy stickybombs, making it look like you placed them will make it like you won't be damaged by them. If teammates come along, run because they will likely be detonated. Walking around the base is effective.
Fooling chance: medium-low if alone, medium-high if on/near a enemy building holding the Wrench
Medic buddy? usually not, if healed, medic will usually only heal you for a few seconds
The engineer disguise is great if you are holding the wrench out while standing on a enemy building, as most players know engineers can't move through their own buildings. This disguise, if alone without a building is better with the Shotgun out. This disguise is 100% speed, letting you chase enemis down for a backstab, and if they catch you, make them think you will soon be Spychecking them.
Support These classes are good for camping in the base, and occasionally out of it, and have a 100% speed, and a fairly small body size.
Fooling chance: low, as you can't fake healing enemies, medium-high if you go behind them with a Medigun Medic buddy? rare, as medics usually don't heal medics unless for humours purposes or they are injured
The medic disguise is a slight slower than actuall medics, (7%). Most players won't notice this, but more experienced players will. This disguise is not good if heading directly at a enemy, but sometimes works very will if them enemy lets you get behind them. If they turn around and you don't heal them, they will usually start spy-checking you. This is a good disguise for walking if you hold out the Bonesaw.
Fooling chance: high
Medic buddy? rare, as medics usually don't heal snipers unless injured The sniper disguise excels at staying in one spot, while you can't fake scoping you can crouch while holding a sniper rifle, and will look identical to a regular sniper crouching while scoped. However, if you move around to much, people will usually try to spy-check you. This disguise is even better if you shift positions every once in a while. This disguise is poor outside of sniping areas usually, unless with the Huntsman.
Fooling chance: low-high, depends on how you act
Medic buddy? low-medium if you act correctly
The spy disguise is a high-risk high-reward disguise, and heavily relies on how you act. The spy disguise works well when you are being healed by a friendly medic, as the opposing team will usually think you tricked them into healing you. Also, you will have a random mask when disguising as a spy, and you will not gain the speed of the class that is on the mask. This can easily reveal that you are a spy. If you act strange around your teammates, and fake trying to get behind them, that is also a good idea. Running directly to or away from a enemy will attract spy-checking generally. Also, disguising as a spy when around a friendly building works to, as you can be next to a dispenser pretending to recharge your cloak, and when the friendly engineer is gone, you can use voice calling to tell your enemies the coast is clear. Also, communication with your teammates will make the disguise work extremely well, as have a friendly scout chase you and shoot you and have bad aim to make it look like he is trying to kill you. This will make it look like you can be damaged by the friendly team, so you look like you are on the enemy team. This is extremely effective on most servers.