Star in One Eye

In manga and anime, a star in a single eye is an old symbol used when a character is hurt or shocked.

It's somewhat similar to the phrase "seeing stars," which in western cartoons is depicted as stars orbiting the character's head. Similarly, in anime, when they're seeing everything spinning, their eyes are drawn as spirals.

Note that having stars in both eyes typically means the character is dreaming of or yearning for something instead.

Character: Hoshizora Miyuki 星空みゆき
Anime: Smile Precure!, スマイルプリキュア！ (Episode 39)

• Examples

Examples

For reference, some examples:

Character: Delia Ketchum, Hanako ハナコ
Anime: Pokémon, ポケットモンスター (Episode 1)

• Context: Ash Ketchum's mother got electrocuted by his electric rat.
• Hair strands sticking out are another symbol typically used when characters are overwhelmed.

Character: Hoshizora Miyuki 星空みゆき
Anime: Smile Precure!, スマイルプリキュア！ (Episode 39)

• Context: a shoe falls on Miyuki's head.

Character: Asagaya Minoa 阿佐ヶ谷未乃愛
Anime: Animegataris, Animegatarizu (Episode 3)

• Context: Minoa is shocked by an unexpected development at the third episode.