Blowfish

Blowfish was a name given to an unknown race of piscene humanoids with a face strongly resembling a blowfish.

History
Toshiko Sato described them as some sort of "landfish" and her scan of one member of the species revealed high levels of algae. (TW: Kiss Kiss, Bang Bang) They seemed to have a weakness to Human pleasures and on Earth committed a wide variety of crimes. (TW: Kiss Kiss, Bang Bang, Fragments)

In the 19th century, Jack Harkness was sent to collect a young Blowfish by Torchwood 3. He was brought back to the Hub, but since there was no way to return him he was simply shot dead by Torchwood agent Alice Guppy, which Harkness objected to. (TW: Fragments)

In the 21st century, another Blowfish was in league with the Time Agent Captain John Hart. He also fell victim to temptation, stealing a sports car and embarking on a drug-fueled joyride through Cardiff. He was tracked down by Torchwood 3. He took hostages in order to bargain for his release, but Jack Harkness was a good shot and calmly used this skill to kill the blowfish with one bullet. (TW: Kiss Kiss, Bang Bang)

Fans have occasionally referred to the member of this species who appears at the beginning of Kiss Kiss, Bang Bang as the "Exposition Blowfish".

Behind the Scenes
The Blowfish had a similar appearance to that of the Marshman