Death in the anime Kamichu! has a short scene with the god of poverty.

Juvia Lockser easily breaks her gloomy facade, only to become perky and the complete opposite to her usual personality (but mostly to Gray though).

However, after she loses her sister Lisanna she becomes a Proper Lady. She basically had the same personality as Natsu.

Mirajane isn't quite 'perky' in her youth - she's Hot-Blooded.

In spite of her dark nature, she seems to smile a lot.

Reiko, the first Devil Hunter Yohko villain.

Misa Amane from Death Note, who wears lots of black, crosses, etc.

D.N.Angel: Towa looks like an Elegant Gothic Lolita, but has the personality of a hyperactive Genki Girl.

In one scene, when she's explaining that the bad smell in a hotel room is from the ooze from rotting corpses she had to clean up in there earlier, she smiles happily, glad to have made things clear, while everybody around her is busy losing their lunch.

Sawyer the Cleaner, from Black Lagoon, qualifies.

The disturbingly cheerful Undertaker in Black Butler.

Her wardrobe consists almost entirely of blacks and reds, she accessorizes with chains and leather, and her Chuunibyou moments involve a lot of flowery talk about 'the darkness' and such, yet she's one of the most chipper and upbeat characters in the cast, especially in contrast with her bandmates. Genki Girl Ako Udagawa from Ban G Dream!.This is technically a different subculture than emo, but they're closely related and scene can be summarized as 'Perky Emo with a little bit of rave culture'. While the trope is sufficient to cover both, a character who is to Emo as this trope is to Goth would essentially be a 'scene or cupcake emo', which are notable for their pink/black stripes. If she's supposed to be attractive, she has a strong chance of being Raven Hair, Ivory Skin. Appropriately, this is a Sister Trope to Elegant Gothic Lolita (referring to an actual subculture mainly popular in Japan). She wears the clothes, but her personality is always cheerful and amiable (occasionally approaching Genki Girl territory).

Sometimes, a singular Goth takes on both personalities. Contrariwise, the Perky Goth, who is almost always female, operates on the principle that dark does not always mean depressing. The stereotypical Goth character, especially in teen television shows, is frequently a Snark Knight or a Deadpan Snarker, someone whose dark clothes and grooming reflect a pessimistic mentality.

Make the emo happy game