"Knowledge" is the ninth episode of Season 2 of Teen Titans Go! and the sixty-first episode overall. It first aired on 21 August 2014 on Cartoon Network.
Starfire is tired of not fitting in with the other Titans, and asks Raven to help her to learn more about human culture. Raven casts a spell to give Starfire all of human knowledge, which turns Starfire into the total bummer.
Robin is standing on the roof of the Titans Tower, and is checking the status of the weather. He crashes into the window of the living room and notifies the other Titans that the weather is absolutely ideal for a beach day. The Titans imagine the possibilities of that day, until Starfire lets out a single yawn. Everyone automatically freaks out, and Starfire inquires why. After Robin quarantines her in a glass tube, the Titans explain how yawns are contagious and cause Earthlings to get sleepy. Just when they thought her yawn didn't affect them, Beast Boy suddenly yawns, causing Robin to encase him in another tube and he falls asleep. Cyborg suddenly yawns as well and fails to stifle it, landing him into a glass tube of his own where he also falls asleep. Robin and Raven express relief, but Raven catches the yawn and is also encased in the tube where she too falls asleep. Robin prepares to head out by himself, but yawns too. He struggles to keep his balance and rips off his shirt for the beach, but collaspes on the ground. The yawn drifts across the room and activates another glass tube that falls onto Robin's upper half.
The day passes, and the Titans wake up at ten in the evening; having missed the only perfect beach day in what Robin calculates will be for another twenty-four years. Ashamed, Starfire apologizes for ruining her teammates' beach day. Cyborg reassures her that it was alright, but she claims it isn't since her misled knowledge of humanity has foiled other attempts for them to have fun. She recalls a time where Beast Boy, Cyborg, and Raven are enjoying a stereo which Beast Boy calls "the bomb" prompting Starfire to mistake it for an actual bomb and throw it out the window. Robin reassures Starfire that they like her how she is, as Beast Boy adds on that knowing things would make her a bummer like Raven. Raven protests that she isn't a bummer, but Robin employs the use of charts and graphs on the TV that prove the level of knowledge one has affects their level of being a bummer. Starfire express her wish to not be a bummer like Raven, and the half-demon teleports away with a sigh.
Later, Raven floats down the hallway when she hears Starfire crying in her room. She questions the Tamaranean, and Starfire reveals that her lack of human knowledge has struck again. Beast Boy enters the room with sizzling eyes; he reveals that Starfire had struck them due to mistaking the meaning behind the term "blind date" and he accidentally crashes through Starfire's window. Starfire calls out to him her apology, but resumes crying. Raven offers to help her by giving her a crash course on human knowledge, yet she wonders if that would make her a bummer. Raven says otherwise, imploring that knowledge is power. Raven begins her lesson by breaking into the song, "Mean What'cha Say," to teach her about popular human phrases. Afterwords, Starfire compliments Raven's song as kitten with the idea that since kittens are good, they will serve as a substitute for the word. Starfire is upset by how silly it began to sound to her, and she started crying again. Raven realizes that teaching Starfire would require more patience than she estimated, and decided to escape the trouble by summoning a magic relic. She instructs Starfire to wear it through the night in order to gain all of human knowledge by morning. Starfire thanks Raven and kicks her out of her room, before excitedly laying in her bed to sleep and absorb all the facts.
The next day, Beast Boy, Cyborg, and Raven are enjoying breakfast when Robin enters, announcing that the day has the perfect qualities for a lake day. Beast Boy, Cyborg, and Raven list all of the advantages of a lake day, but Starfire - now donned in glasses - interrupts by sprouting facts about pollution. Beast Boy questions why they're talking about numbers while Cyborg mentions that they bum him out, before zapping Starfire's facts with his finger. Robin looks back and forth between Raven and Starfire, and deduces that Raven had something to do with Starfire's transformation. Raven once again says that knowledge is power and Starfire reassures that her knowledge on human culture will now impede her from ruining more fun, but Robin yells that Starfire's ruined lake day with her knowledge. Raven argues that knowledge will make her smarter, but Cyborg adds that it has the possibility of making her a bummer. She doubts his prediction, but experiences everything that proves the theory correct. While, Raven is reading a book, Starfire floats by and spoils the ending. While Raven is meditating, Starfire tells Raven that meditation can cause muscle spasms and hallucinations. Raven is playing with her Pretty Pretty Pegasus dolls in the forest, when Starfire tells her that the dolls are for babies. Throughout these occurrences, Robin, Cyborg, and Beast Boy shout "BUMMER!" following Starfire's facts.
On the couch, Raven admits to the male Titans that Starfire has become a bummer. The Tamaranean enters with an surprisingly over-sized brain. The men freak out at the new transformation, and Raven reveals that the more knowledge she obtains through the necklace will cause her brain to expand which would eventually explode. She summons a ship for the four Titans and shrinks it so that they can enter Starfire's brain through her ear. While voyaging through her head, Beast Boy spots the abundance of neurons which Raven deems unnatural and rapidly growing. Robin resolves to destroy them and shoots several of them in half, but they simply reattach themselves. Beast Boy notes this, causing Raven to reveal that they'll have to attack the source.
The ship arrives at Starfire's brain, where they encounter the source; which resembles Starfire. She tells them that she contains knowledge, facts, and trivia which Cyborg deduces to be the reasoning behind Starfire becoming a bummer. The source agrees and reveals she will turn Starfire into an official bummer if her plans remain unaltered. Robin retaliates by firing missiles from the ship. The source reveals that seventy-five percent of missiles never reach their target, and the missiles veer off course. Robin shoots lasers at her, but the source is unaffected as she reveals that laser technology is not advanced enough to deal real damage. Robin realizes that the source is sprouting facts to counter them as she unleashes a powerful brain blast. Raven realizes that they'll have to fight knowledge with ignorance. She, Robin, and Cyborg interpret the source's sayings literally as Starfire would do. The source is greatly weakened by the Titans' ignorance, and Robin finishes her off by informing her that the Titans win one hundred percent of the time, and fires a laser that obliterates her.
The ship flies out of Starfire's ear and expands enough for the Titans to exit before it vanishes. Robin asks Starfire how she feels, and she explains that her head feels better. It continues to shrink in size, until the glasses dissipate and the charm splits in two. Robin, Beast Boy, and Cyborg cheer, as Raven apologizes for taking the easy route instead of teaching her with normal supplies. She begins to list them off, but is interrupted by Robin, Beast Boy, and Cyborg calling her a bummer.
The song Beast Boy, Cyborg, and Raven were dancing to was the Harlem Shake.
Raven's line of "Knowledge is power" and her song "Mean What'cha Say" and it's accompanying animation alludes to Schoolhouse Rock!, animated short films (and later videos) that used musical accompaniment to teach educational topics such as grammar, history, etc.
A Triforce from the Nintendo video game franchise, The Legend of Zelda, appears on Starfire's magic knowledge necklace.
Raven is reading a Tale of Flame and Snow, alluding to the popular epic fantasy book series by George R.R. Martin, A Song of Ice and Fire, which is infamous for the deaths of main characters.
Starfire was wrong when she said 46% of lakes are polluted. In real life, 47% of lakes are polluted.
Starfire told Raven that the pegasus figures she was playing with were for babies. In real life toys like that would pose a choking hazard for children under 3 years old. Also, the targeted age group is around 5-15 year old girls.
The Image Gallery for Knowledge may be viewed here.