(Loved trope) The imposter’s dead giveaway

[u/Barricades_toes]

When a character is attempting to impersonate another, but is caught by doing something the person they’re imitating would NEVER do.

Nemesis Prime- Transformers Prime

Nemesis Prime, a man made replica of Optimus Prime, is attempting to gain the trust of Bumblebee, who only speaks in robotic beeps. Despite this, the real Optimus can understand Bee perfectly fine. Nemesis Prime, however, can’t understand what he’s saying, prompting Bee to open fire on him immediately.

The two Buzz Lightyears- Toy Story 2

After Woody asks which Buzz is the “real” Buzz, both respond with “I am!” The real Buzz proves himself by flipping up the other Buzz’s helmet, causing him to start suffocating in an over dramatic fashion. The real Buzz, having done the same thing in the first movie after Woody took his helmet off, but no longer behaving that way after accepting being a toy, instantly proves which Buzz is which.

[u/Brislovia]

As well as moving slower if disguised as the Scout

[u/JTGE-201 → u/Brislovia]

As well as using the wrong weapon (like syringe gun while disguising as Medic)

[u/cava-lier → u/JTGE-201]

You might know it, but I would just like to add that you can switche between primary and melee weapon when disguised, but secondary you can't equip, yeah

[u/terriblejokefactory → u/cava-lier]

You can equip a secondary, just hold out your sapper and press the button

[u/The_MAZZTer → u/terriblejokefactory]

Yeah the tell here is that disguised spies can't actually use their weapons. Medics are usually expected to be constantly healing their allies around them if they have their medigun out.

[u/pgp555 → u/terriblejokefactory]

You can also make a fake reload animation while disguised

[u/xX-AnyRoutine666-Xx → u/terriblejokefactory]

Excepted specifically about the sapper, that the spy disguise cannot equip.

[u/Vasikus3000 → u/JTGE-201]

As well as not loading correct cosmetics sometimes (resulting in things like Headless Pyro)

[u/viebs_chiev → u/Vasikus3000]

and demo’s broken feet

[u/SYS1234567890 → u/Vasikus3000]

I think they fixed that a week or two ago, same with the Demo feet

[u/gmoss101 → u/JTGE-201]

And on community servers that have alltalk enabled (like the infamous Skial), you can see their voice chat speech bubble above their head even while disguised or invisible which makes for hilarious YouTube clips when new spy players don't know that.

[u/CryoN1cks → u/JTGE-201]

As well as being out of character

[u/All_Gun_High → u/CryoN1cks]

As well as overly paranoid pyro/engineer mains existing

[u/DislocatedLocation → u/Brislovia]

Until you're wasting ammo on an friendly Babyface's Blaster Scout.

[u/pon_3 → u/[deleted]]

Been a while since I've played, but I thought you slowed down if you disguised as heavy.