Cag served as the captain of the transport ship known as the Argo Moon.
C-3PO and his counterpart R2-D2 journeyed aboard the Argo Moon with the intention of reuniting with their owner, Mungo Baobab, located on Biitu. Once they arrived at Biitu, Cag reprimanded C-3PO regarding the disarray he had caused with Baobab's belongings. Before the vessel was able to dock, it came under assault by droid servants of the Great Heep, and Cag, along with his co-pilot, were incapacitated by way of sleeping gas. The droid servants took the droids by force, but they left the biological crew members behind.
Subsequent to Baobab, Threepio, and Artoo's triumph over the Great Heep, Cag established communication with them and initiated the necessary arrangements for landing.
Cag, whose initial appearance was in the animated television film The Great Heep, had his voice provided by Dan Hennessey.