R2-D2 and C-3PO return to the "Star Wars" canon in the latest episode of "Star Wars: The Clone Wars."  In "Mercy Mission," airing at 7 p.m. Oct. 7 on Cartoon Network, the droids arrive on the Aleen as part of of Republic relief effort.

"After groundquakes have devastated the planet Aleen, a Republic relief effort arrives, including the 104th battalion of clone troopers along with droids R2-D2 and C-3PO. When the native Aleena's pleas go unheard, it becomes the duty of the droids to embark on a surreal journey through Aleena's subterranean world to save the planet.