"Mouth Hole" is the twenty-fifth episode of Season 2 of Teen Titans Go! and the seventy-seventh episode overall. It first aired on 8 January 2015 on Cartoon Network.
Robin goes on a quest to gain a new power: whistling.
The Teen Titans emerge from the Pacific Ocean outside of H.I.V.E. Tower. They arrive at the front doors where Robin reminds the Titans that the H.I.V.E. Five is plotting something and that they're going to discover what their plans are while he stands guard. He tells them to keep their communicators handy, but Beast Boy admits that that would be a problem as his was broken when Raven threw him across the room for bugging her with it. Cyborg suggests that Robin just whistles to alert them to the H.I.V.E. and they head inside. Robin nervously reassures himself that it's just whistling when the H.I.V.E. Five Monster Truck appears behind him. Inside, Cyborg is downloading the H.I.V.E.'s evil plans when they hear noises. The Titans each try to guess what the noise sounds like when the H.I.V.E. capture Robin and appear behind them. They beat the Titans and throw them out of their tower.
Back at Titans Tower, Cyborg questions Robin and asks if he heard him when he said to whistle in case the H.I.V.E. showed up. Robin answers that he was whistling, but gives excuses as to why they didn't hear it. Raven asks if he can even whistle and Robin claims that he can, but fails and spits saliva over his teammates. Cyborg asks how would Robin ever call a cab or dog and demonstrates by whistling, calling a taxi cab and a dog-transformed Beast Boy. Robin claims that he would never devote his life to something as insignificant as whistling, but changes his mind when Starfire volunteers to teach him.
On the rooftop of Titans Tower, Starfire compliments the weather as perfect for whistling. She tells Robin to observe her and begins whistling, calling birds to her side and entrancing Robin. After she lands, Robin compliments her features, but Starfire assumes that he is describing whistling. She tells him to place his lips together and Robin puckers them and leans in, asking if he's doing it right. Starfire grabs his lips and tells him that it's like this. She encourages him to give a whistle, but Robin struggles to breathe and escape her grasp. He falls on the floor and Starfire praises him for his effort while Robin calls her a wonderful teacher.
Later, Beast Boy opens the door to the refrigerator when he hears a noise mimicking his actions. After he closes the door, the noise appears again. He asks Cyborg what the noise is, but Cyborg claims to not know. Beast Boy opens a pan on the stove and the noise repeats itself. Both Titans attempt to leave the kitchen, but their actions continue to be mimicked by whistles. Beast Boy transforms into a bat and a koala while Cyborg goes up and down, but the noise doesn't stop. They claim to not be able to take it anymore when Starfire and Raven enter the kitchen. Raven hears a wolf whistle and slaps Beast Boy for it, but he claims it wasn't from him. Robin emerges from a plant in the corner and claims it was all him. Starfire praises Robin for learning how to whistle and he claims to have learned how to whistle, but takes out a slide whistle. Beast Boy claims that that is not whistling, but Robin explains that like all his shortcomings, he adopted a gadget to help him. Cyborg explains that whistling isn't like the powers Robin doesn't have and Starfire agrees. Raven decides, that to teach Robin, they must adopt total immersion therapy.
At the living room, Robin questions the Titans for their decision to only use whistling to communicate with each other, claiming it to be impossible. However, the four prove him wrong when they share a joke using only whistles. Robin begins to question them, but the four begin performing a song using only whistling. Robin is unable to do so. Frustrated, Robin interrupts them and reminds them that the H.I.V.E. is plotting something, but Raven questions who's going to lead them against him. Robin says he would as he is their leader, but Beast Boy jokes that he can't even lead his lips into whistling. Robin agrees and begs the Titans to help him. Raven says that there is one last option and begins to read a legend from Ancient Legends in whistles until Robin tells her to just read it. She explains that he must travel to the Mystical Mounds of Gomera and find the Master of Whistles.
Robin enters a castle and spots a teapot. He asks to see the Master of Whistles and the teapot agrees but offers a refreshment before taking him to see the master. Robin claims that he has to see the master and has no time for speaking with a teapot. The teapot questions if all he sees is a teapot and he points out her handle and spout. Angered, the teapot whistles and slams him into the door. Robin recognizes the teapot as the master and wishes that he could whistle like her. She claims that he can and offers him the drink once more. Robin takes it, but gags and questions what drink it was. The teapot explains that it's hot sauce and Robin whistles to let the steam out. She explains that the hot sauce unblocked his doubt and that training can begin.
On the mounds, the teapot blows a rock over to Robin, but he is unable to do so. He attempts to blow a rock into the air, and performs push-ups with his mouth. The teapot demonstrates the act of summoning a fist with whistling to break a board, but Robin is unable to do so. She then straps him to a wheel and whistles rocks as Robin and he succeeds in stopping one by whistling. Eventually, Robin is able to roll the rocks back and forth, blow boulders into the air, perform push-ups with whistling, and control his fist whistle to break the boards. He receives an alert on his communicator informing him that the H.I.V.E. captured the Titans and attempts to leave to rescue them. The teapot blocks him and claims he isn't ready before summoning a fist to attack, but it is stopped by Robin's whistle fist. She relents and tells him to go save his friends.
At the H.I.V.E. Tower, the Titans are chained to the ceiling with Gizmo announcing that their super secret weapon, a death laser, is complete and attempts to shoot the Titans with it. Robin enters the tower and Gizmo orders his teammates to get him. Mammoth charges Robin, but he calmly applies chapstick on his lips and whistles himself into the air, before using a whistle fist to crush him. Raven notes that the teapot taught him her secrets and he nods before See-More fires a laser. Robin whistles himself toward him and applies a shield to block the laser before using a whistle finger to poke him in the eye and a whistle foot to kick Jinx. He whistles to summon a horse head to slam into See-More and the hose rear to slam into Jinx. Billy Numerous duplicates himself and surrounds Robin, but he summons a whistle machine gun and shoots down each clone.
While his back is turned, Gizmo fires the death laser at Robin, but Robin counters with his own whistle blast. However, the laser nears Robin and he begins to worry until he imagines the Master of Whistles telling him to use his steam. Robin blows harder and destroys the laser, sending Gizmo and the death laser out of the tower. He uses a whistle to break the Titans' chains and another for them to land safely and to cut their bonds. Starfire approaches Robin and claims to never have known how powerful whistles can be. Robin agrees that they have the power to destroy, but also the power to enchant. He surrounds Starfire with winds and propels himself into the air. They dance in the air while Beast Boy remarks that they look so beautiful. Robin catches Starfire into her arms and she asks for him to kiss her. They begin to lean in as the Titans gasp in anticipation.
For a full transcript of "Mouth Hole", click here.
Cyborg tells Robin to "give a little whistle", a reference to the song from Disney's Pinocchio.
The Master of Whistles bears resemblance to Mrs. Potts from Beauty and the Beast.
The first few lines of "I'm a Little Teapot" are exchanged by Robin and the Master of Whistles.
Robin claims that the drink is something to "wet my whistle", a reference to the 1983 song by Midnight Star.
Cyborg tells Robin to "whistle while you work", a reference to the song from Disney's Snow White and the Seven Dwarfs.
The Titans communicating with whistles may be a reference to the children's show Clangers.
When Robin is nearly defeated by Gizmo, an image of the Master of Whistles appears and appears to talk in Robin's head. She says, "Use your steam, Robin," which is a reference to Star Wars Episode IV: A New Hope, in which Yoda talks to Luke in his head, saying "Use the Force, Luke."
Continuity error: Robin should already know how to whistle as he whistled to get the attention of Batman's bats in "Sidekick" and before spotting the fire in "The Best Robin".
The Image Gallery for Mouth Hole may be viewed here.