Secret Invasion has not solved even a single existing mystery of the MCU but it is happily adding more to the list. And recognizing who is a Skrull and who isn’t already tops it.
In the MCU, differentiating between a Skrull and the human it is pretending to be — whether via a mere glance or a grueling conversation — is impossible. We have been told that if their DNA is tested, they will be the same. And while Carol managed to figure out whether she was chatting with the real Nick Fury by interrogating him about his life, Secret Invasion has shot that trick in its foot as well, as Skrulls now keep the original humans they are copying on a comatose leash, copy-pasting their memories, thus leaving no way to detect if they are the real deal.
But let’s not give up hope as amid its fictional and badly sketched (present and future) plotline chaos, Secret Invasion does answer the dilemma.
How to differentiate between a Skrull and a human in the MCU?
Yes, we already know that upon dying a Skrull sheds their human mask and reverts back to their original form. But come on, if you were to live your dream and land in the Marvel Cinematic Universe, you can’t possibly go around shooting people whose credibility and personality seems the tiniest bit shifty.
The answer hides in Marvel’s most gruesome scene ever — Olivia Coleman’s Sonya gleefully chopping off the Skrull’s finger in episode two.
After Chris Pratt’s Star-Lord breaking the Marvel pact to not say the f-word, an MCU series openly depicting such a gory sequence left many brains on pause as they tried to wrap their heads around it (while admiring Coleman’s flawless performance). In all that chaos, you may have not seen the Skrull’s severed finger change into his original green scaly skin the second it is removed.
Now, that ain’t a pretty way to know who a Skrull is either, but at least one doesn’t have to go around putting a bullet in everyone acting shifty. And for now, this is the only non-deadly way of detecting if a human being is a Skrull in disguise.