Welcome Back Goku (オッス!! ひさしぶり... 帰って来た孫悟空, Ossu!! Hisashiburi... Kaettekita Son Goku) is the fourth episode of the Trunks Saga and the one hundred twenty-first overall episode in the uncut Dragon Ball Z series. The episode first aired on December 18, 1991. Its original American air date was September 7, 2000.
This episode begins with the mysterious youth slicing the vivisected Frieza into many pieces and destroying him with an energy blast. The Z Fighters have seen Frieza getting cut up into pieces and Bulma thinks that Goku has finally showed up just in the nick of time and Gohan tells the others that he is a Super Saiyan, but he's not Goku. The stranger sets his sights on King Cold himself. The tyrant tries bribing the Super Saiyan by offering him Frieza's place at his side. He refuses, and King Cold decides to change the subject, asking for the strange visitor's sword. The youth gives him the sword, but King Cold had little real interest in it, believing him powerless without his weapon. After blocking a Dirty Slash by the tyrant, the youth fires off a God Breaker energy wave, which pierced King Cold's stomach. He pleas with the boy not to destroy him, but, with another energy blast, Frieza's father is no more. Another attack destroys King Cold's spaceship, much to the amazement of the Z Fighters.
The youth then tells the others that he is going off someplace to wait for Goku, who will be arriving soon. They follow the boy. When they reach the site where the youth believes Goku will land, he produces a refrigerator, stocked with various sodas and juices, which the Z Fighters take while they wait. They ask many questions, which the boy politely refuses to answer. As they wait, they speculate on the identity of the boy; Bulma sees a resemblance to Vegeta, while Tien Shinhan thinks the boy met Goku somewhere in space, though Chiaotzu points out that the stranger said he had never met him. He seems particularly interested in Vegeta, frequently looking over at him. Vegeta, for his part, refuses to believe that the boy is a Saiyan, since he, Goku and Gohan are the only ones left and also tells the boy that all Saiyans have black hair, but the boy still refuses to explain. Goku finally lands in one of the Ginyu Force's pods. He is shocked but glad to see everyone there, curious as to how they knew when and where to find him.
- Mecha Frieza and King Cold are killed by Trunks.
- Goku returns to Earth.
- Future Trunks (Super Saiyan) vs. King Cold
"I say that without this sword you're nothing! That's what I believe!"
"So much for your theory. You should know that a weapon doesn't make the man."
- When Future Trunks slices Frieza in half, he appears to be hollow, however upon slicing him into several pieces Frieza appears to have flesh (even his mechanical body parts).
- When King Cold is holding Future Trunks' sword, the sword is much bigger than Future Trunks, but when he gets it back, it returns to its normal size.
- King Cold begging for his life is filler. Additionally, his begging is different in the English and Japanese versions. In the English versions, he said Frieza was the truly evil one and he only wanted peace. In the Japanese version, he once again tries to bribe Trunks by offering him planets to rule.
- The box Ox-King is holding when he and Chi-Chi bring back Gohan's new study bed is spelled as "MY STADY". This is a translation error due to Japanese pronunciations not having an "uh" sound, using the "ah" sound instead. Thus, "study" in Japanese would be pronounced "stahdy," which could be mistakenly spelled "stady" when translated to English.
- When Krillin holds his left hand up in apology to Vegeta for kicking his empty soda can, his wristband disappears.
- In the original dub, after Goku arrives on Earth, the traditional Closing Theme music plays in the background. In the remastered dub, the Closing Theme is replaced with a peaceful sounding theme heard a few times in the Captain Ginyu Saga and Frieza Saga.
- While Future Trunks is leading Goku's friends to the place where Goku will arrive, one of the scenes showing Future Trunks is missing his Capsule Corp logo on his left shoulder.