A cold planet where a transporter fault splits Kirk in two while Sulu's landing party is left stranded on the surface in The Enemy Within.
Alfa 177 is a planet surveyed by the Enterprise in The Enemy Within. An unusual magnetic ore from its surface damages the transporter, which then divides beings beaming up into two halves, one gentle and indecisive and the other savage. The first sign is a native doglike animal that returns as two creatures.
Kirk is split next, and with the transporter out of service, Sulu and the rest of the landing party are stranded on the surface as night falls and temperatures plunge far below freezing. Their worsening condition gives Scott and Spock a deadline to repair the system and reunite the captain.