Surprised Pikachu, also known as Shocked Pikachu, refers to a screenshot from the Pokémon anime of the character Pikachu with its mouth agape, as though it were surprised at something. In the autumn of 2018, the image was used as a reaction image paired with captions where a set-up leads to a predictable outcome that nevertheless leaves one surprised.
Surprised Pikachu automatically gives an example of :o