The Grumpy Converter from Bluxte is a strange form of life which is capable of making hundreds of copies of any object it ingests; including several forms of currency, which makes it extremely useful in interstellar markets. It physically resembles a rat-sized, feathered armadillo.
It is extremely rare and hard to capture, and its metabolism has been compared, in terms of energy, to a nuclear reactor. It is also a clever creature, and typically reluctant to collaborate, thus earning its name. When exhausted after laboring, the Converter can be attached to almost any type of energy source to regain its vitality.
- Valérian and Laureline:
- Ambassador of the Shadows (1975)
- The Circles of Power (1994)
- Hostages of the Ultralum (1996)
- The Time Opener (2010)
- The Inhabitants of the Sky: The Cosmic Atlas of Valérian and Laureline (1991)
- Valerian and the City of a Thousand Planets (2017; as "Mül Converter")
- The Grumpy Converter comes from the same planet as the Spiglic, yet differs radically in temperament as the latter is widely known for its cheerful and tranquil nature.
- The Grumpy Converter can also be compared to the Babel Fish from Douglas Adams' The Hitchhiker's Guide to the Galaxy series, both being life forms whose properties have implausibly practical value, to the point that it is hard to imagine how they could have evolved naturally.
- The Cosmic Atlas of Valérian and Laureline provides some background to the natural history of this species, revealing that the natural populations use their abilities to multiply the fruits and seeds they feed on, perpetually recycling their food supply. The issue of how is that consistent with the laws of thermodynamics is not addressed.
- In the Cosmic Atlas, it is further explained that the internal workings of the Grumpy Converter have never been observed, as their bodies mysteriously dissolve whenever a dissection or autopsy is attempted.