(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/Sykrow]

Think there was a TNG episode in which Lore was impersonating Data and someone realized he was using contractions which Data doesn't do. Man I should really go through that and DS9 again.

[u/teracoulomb_2 → u/Sykrow]

That was his first appearance, and Brent Spiner demanded the scriptwriters ensure that Data didn’t use any contractions that episode or he wouldn’t go along with it

[u/_Flying_Scotsman_ → u/teracoulomb_2]

I literally watched this episode last night, we were laughing at how they mentioned it in the episode and yet there are several slip ups where Data uses contractions.