The dwarf carbon ( dC ) star SDSS J112801.67+004034.6 has an unusually high radial velocity , 531 \pm 4 km s ^ { -1 } .
We present proper motion and new spectroscopic observations which imply a large Galactic rest frame velocity , 425 \pm 9 km s ^ { -1 } .
Several other SDSS dC stars are also inferred to have very high galactocentric velocities , again each based on both high heliocentric radial velocity and also confidently detected proper motions .
Extreme velocities and the presence of C _ { 2 } bands in the spectra of dwarf stars are both rare .
Passage near the Galactic center can accelerate stars to such extreme velocities , but the large orbital angular momentum of SDSS J1128 precludes this explanation .
Ejection from a supernova in a binary system or disruption of a binary by other stars are possibilities , particularly as dC stars are thought to obtain their photospheric C _ { 2 } via mass transfer from an evolved companion .