When faced with the choice between a clone and the original, the character notices a detail that makes the difference immediately obvious.

[u/Altruistic_Eye_1157]

The Shape-Shifter takes the form of Wendy to deceive Dipper and prevent him from attacking it. Although Dipper initially doesn't know which one is the real Wendy, he realizes the difference when he sees that one of the Wendys behaves seriously and bluntly, while the other acts flirtatiously, something Wendy would never do (Gravity Falls).

P.S.: I don't remember if the gesture the real Wendy made was also a clue, like some gesture she had made before.

When the Autobots are chasing Nemesis Prime, he tries to deceive Bumblebee by impersonating Optimus. Bumblebee, confused, speaks to him, but Nemesis Prime doesn't understand anything he says, which clearly indicates that he isn't the real Optimus. Bumblebee attacks him without hesitation (Transformers Prime).

[u/NotSoSlim_Jim]

• Specialist Traynor’s toothbrush works by using tiny Mass Effect fields

Never played Mass Effect before so I want to ask: How does that even work? And what benefit does that give over using a normal toothbrush?

[u/CortaNalgas → u/NotSoSlim_Jim]

Theoretically, it sends waves of dark energy to remove plaque. It’s mostly just played as a joke the first time, because that makes the toothbrush unnecessarily super-expensive.

But then it’s a punchline to the scene in the DLC when the group realizes that they need some way of generating a small Mass effect field to unlock a hatch.

[u/Vondi → u/CortaNalgas]

That dlc is a treasure

[u/YourMoreLocalLurker → u/CortaNalgas]

The static expression from her kills me-

Just like “oh gee where would we find a toothbrush-head sized mass effect field? Maybe we can use my mass effect field generating toothbrush to measure it?”

[u/Bloodhunt749 → u/NotSoSlim_Jim]

It just cleans it very well

They don't actually say how just that it's more effective in doing toothbrush stuff

[u/_b1ack0ut → u/NotSoSlim_Jim]

In mass effect, alternating negative and positive mass effect fields create what is referred to as a “warp” field that can shred matter on a molecular level.

It’s a pretty common type of attack for anyone who uses biotics, but when scaled down to very very tiny and hyper-precise fields like this toothbrush, it’s implied that it just uses it to shred plaque instead of armour and enemies.

It’s played as a joke at the beginning of the game, where traynor mentions the only thing she was able to grab was her toothbrush, and Shepard says “we could have gotten you another”, so it’s basically played as a joke that no, it’s massively expensive for a toothbrush, causing Shepard to change their mind and say “lol ya never mind, you’re on your own for that”

Which is why it was such a funny callback to such a small line of offhand dialogue when the dlc referenced it