Although there are a few pokemon, such as Slowpoke, which evolve in conjunction with other species, Karrablast is the only one of these pokemon known to evolve through theft. To become an Escavalier, a Karrablast must steal a Shelmet's shell. The Shelmet resent this, although it causes them to evolve as well, for a Shelmet's weakness has given them cowardice, and they see only defenselessness in evolving.

For wild Karrablast, evolution is a great challenge, for although Shelmet are technically bugs, a Karrablast's corrosive acid - their primary weapon in this phase - can not penetrate Shelmet's steel shells. Few wild Karrablast succeed in their chase, and the determination and futility of their efforts has inspired many a classic Unovan cartoon, where characters based on the Karrablast will attempt a series of elaborate, intelligent ruses to chase Shelmet from their shells, which can only ever succeed when the cartoonist is retiring their characters. In reality, Karrablast are not nearly so creative; although they will take every opportunity offered, they are rarely able to create their own. Shelmet are too heavy, and Karrablast's limbs too weak, to push them out while sleeping, and Karrablast efforts to terrify them typically lead only to the Shelmet closing their shells.

The most reliable way for a Karrablast to evolve is with the aid of a third species, Man, who conspire to switch their Shelmet and Karrablast with one another for the sake of evolution. Most Karrablast, after many failed efforts, in time come to understand this fact and eagerly seek out capture. These pokemon have even been known to climb into empty pokeballs while their trainer is sleeping – which for all its difficulty is far easier than robbing a Shelmet!