Gintama' - episode 34 - 20 Nov, 2011

Overall episode number: 235 Gintoki and Sakamoto reveal themselves and attack the Double Dragon generals. Meanwhile, Elizabeth has launched in the Gunsam to battle Dark Vader in a duel to the death. Elizabeth is helpless against Dark Vader. That is when Katsura arrives to protect his friend's back! (Source: Crunchyroll)