This is a classic "React" video trope in the Gacha community. Since Adrienette (Adrien and Marinette) finally revealing their identities is a high-stakes moment, the reactions usually range from shock to "I knew it!"
Miraculous Holders React to Adrienette Identity Reveal (The Confession) Scene 1: The Gathering This is a classic "React" video trope in the Gacha community
(Rubbing the back of his neck) "Guess the cat's out of the bag?" Editing Tips for Gacha Club: This is a classic "React" video trope in the Gacha community