Greenman vs. Totsaurus (グリーンマン対トットザウルス, Gurīnman tai Tottozaurusu?) is the eleventh episode of Go! Greenman.
Hoping to please his master, Tonchiki bows to Maoh and reassures him by telling him of a plan. Tonchiki looks to some children who are playing baseball in a small field. The children are stopped in their tracks when they experience an earthquake, which also causes landslides that destroy small buildings. The culprit soon reveals himself to be Totsaurus, whose presence send the kids running. Two of them trip in the field, and are noticed by Tonchiki who runs toward them with a rope. The remaining children use their Green Calls to summon Greenman. Tonchiki begins to tie up the two kids who tripped, and Greenman flies in, landing directly in front of Totsaurus. Not realizing that the children are ties, Greenman starts to fight Totsaurus while Tonchiki pulls them away. Greenman continues to fight with the monster, often utilizing his surroundings by knocking Totsaurus into a mountain face. As Greenman pushes Totsaurus down again, he turns to see Tonchiki kidnapping the two children. He quickly draws an Ear Boomerang, severing the rope and letting the children free. Fearing Totsaurus's defeat, Maoh orders him to use his weapon. Totsaurus opens up his mouth and fires a large rock-like object towards Greenman. It begins to emit a harmful, white gas which weakens Greenman. One of the children who is looking on to the fight, throws a Green Call to him. He picks it up and activates it, strengthening himself. Greenman jumps up and utters the phrase "Greenman Giant Machine Change", making him grow to giant size. Tonchiki quickly makes Totsaurus grow as well, and they attack each other once more. Meanwhile, the two kids who had been trying to escape, continue to be chased with a rope still around their waists. Greenman tries to fire another Ear Boomerang to them, but is stopped by Totsaurus who spits another object. Now with Greenman weakened by the ball's white smoke, Tonchiki uses a spell to make the children freeze in place. Greenman continues to attempt fighting, but his efforts prove useless, as he is thrown to the ground by Totsaurus. He manages to get up again, and punch at the monster, before dodging yet another gas ball, and summoning the Greenman Stick. Greenman uses Stick Beam to inflict damage on Totsaurus and greatly weakens him with the weapon. Eventually, the Breaster missiles destroy Totsaurus, and a startled Tonchiki runs away, dropping the rope and freeing the tied up kids again.
When Greenman was in giant form and saw the children tied up, he attempted to throw an Ear Boomerang. Being in giant form, his boomerang would also be giant. If he had managed to throw it, it would have most likely injured or killed the children, being as gigantic and highly explosive it is.
This episode introduces Tonchiki's ability to freeze humans in place. Oddly enough, this ability is never used again in the entirety of the series, despite its usefulness.
At the end of the episode, Greenman flies away to space, leaving the two tied up children with a rope around their bodies. This seems very unlike him, as Greenman is often seen to go out of his way to make sure the children are happy.