Source: SpongeBob SquarePants
SpongeBob SquarePants is shown in close-up holding open a briefcase that emits a bright, magical golden glow from inside, while he looks down at it with a pleased or curious expression.
This template is used to represent the discovery of something precious, amazing, surprising, or highly desirable. The blank space inside the briefcase is meant to be filled with whatever content the user is 'revealing'.
What makes "SpongeBob opening mysterious glowing briefcase" from SpongeBob SquarePants stick is that the expression and timing are doing more work than the words alone. Stripped from its original narrative, it became a versatile template meme that people use whenever they need to convey shock and disbelief faster than typing allows.
