The exact origin of this clip is not widely documented, so its life online is mainly as a reaction sound rather than a quoted scene. The phrase works because 'Brandon, are you serious?' names a specific person while expressing a universal feeling, which lets creators apply it to any character or friend in a video. It circulates on soundboards and in short edits where a single line needs to signal disbelief instantly, and its very short length makes it easy to reuse without covering dialogue.