Suddenly Bilingual

Occasionally in sitcoms or comedy series, a character will speak fluently in a foreign language, briefly and to the slight surprise of others, for comedic effect. Why this character can speak Tibetan or Russian or whatever is never discussed and, often, never questioned. Note that this is not referring to a character who had an unknown history of working with language- it simply occurs once and never again.

"Brian: Hola, me llamo es Brian ... Nosotros queremos ir con ustedes.. uhhhh ... Hispanic Guy: Hey, that was pretty good, except when you said "me llamo es Brian," you don't need the "es," just "me llamo Brian." Brian: Oh, oh you speak English! Hispanic Guy: No, just that first speech and this one explaining it. Brian: You .... you're kidding me, right? Hispanic Guy: Que?"
 * In one episode of Lost, it turns out that Juliet can speak Latin. Apparently, all Others are taught Latin. This is never mentioned again.
 * A later-justified example occured in Gunnerkrigg Court, when Antimony turns out to speak conversational Polish and, later, at least a bit of Spanish. Several storylines later, it's revealed - in an offhand comment - that she basically grew up with a bunch of Psychopomps, who taught her each of their languages (judicous use of time-stopping was apparently used). This presumably means that she also speaks Egyptian, Greek, and Hindi, along with god (of death) knows how many other languages.
 * Kenneth from Thirty Rock is revealed to be fluent in Latin for a quick gag.
 * However, a Running Gag is to imply that he is possibly immortal, or at least very very old. He could have easily been a medieval monk or something.
 * In Danny Phantom Tucker is suddenly revealed to be able to speak some Esperanto, though it does come up several times later on.
 * In Sky High, Anti-Hero Warren Peace can speak Cantonese (It gives the impression that he's fluent but this troper who speaks it as a first language can say that unfortunately he doesn't speak it very well...). This is very convenient, because he works at a Chinese restaurant. whether he learned it at work or if he already knew it is never explained, and he certainly doesn't need it for anything else over the course of the movie.
 * In the Phineas and Ferb special "Summer Belongs To You!", the Dumb Muscle bully Buford suddenly speaks fluent, and polite, French to a waiter in Paris. Then he orders Baljeet never to tell anyone.
 * In one episode of The New Statesman, Alan B'Stard is on trial, and one of his fake witnesses is pretending to be a chief of a native South American tribe. It turns out that the prosecuting lawyer can speak the language of that tribe, having been a fag for the tribe's high chief while they were both at Eton College.
 * Bart Simpson Lampshades this one in an episode of The Simpsons, where he goes to France in an exchange program and starts suddenly speaking French in the middle of a sentence.
 * From King of the Hill, Bill speaks French because he grew up in an upper class Cajun family in Louisiana. Peggy lampshades this and Bill seemed genuinely surprised that he spoke French too, or that the language he was speaking was French it's not quite clear.
 * Justified in Toy Story 3 with
 * Bubbles in The Powerpuff Girls can speak Spanish, though she doesn't have the chance much. Why can she? Because each of the girls has one unique superpower. That's hers.
 * Bubbles' language skills were expanded from this one-episode gag to speaking any language - up to and including squirrel.
 * Used on The Office: when Karen calls a company in Canada looking for her favorite chips, she speaks in perfect French. Never seen before that scene or since.
 * On iCarly, especially in the second and third seasons, Freddy often bursts into Gratuitous Spanish. This implies that he is somewhat bilingual.
 * Family Guy: Brian is riding in the back of a truck and tries to talk to a Hispanic passenger, and is struggling with his junior-high Spanish:

"Face: You speak Swahili? Murdock: You don't?"
 * In Teen Titans: Trouble in Tokyo, Starfire becomes able to speak Japanese by kissing a local.
 * Jenny from My Life as a Teenage Robot has several language discs that enable her to speak in foreign tongues. In one episode she loses her English disc while fighing a Kaiju in Japan and is stuck speaking Japanese for the rest of the episode.
 * In The a Team, a mix-up with forged passports results in Murdoc needing to pass himself off as an African. His teammates, realizing the mix-up, figure their cover's blown and start scoping out emergency exits--then Murdock starts chatting with the Customs officer in Swahili. Later:


 * This might be a Mythology Gag referring to a literal example in the original series. In one episode the A-Team went up against a triad running a protection racket. At one point said triad left a message on a wall in Mandarin, which Murdock translated easily. Everyone stared at him, then he mentioned how one night he went to bed with a splitting headache and woke up able to speak Mandarin.
 * In Generator Rex, the main character suffers from amnesia but is obviously non-Caucasian, so his occasional use of Gratuitous Spanish is expected. Then he finds in one episode that he can also speak Chinese. Possibly justified in that
 * Castle speaks Chinese in one episode. His only explanation is that he learned the language "from this TV show I used to love". It's never mentioned again.
 * In The Vicar of Dibley, Alice and Hugo are suddenly able to speak Hebrew in order to be cast as Mary and Joseph. It is hilarious.
 * On Dollhouse Actives can speak multiple languages when they're imprinted with new minds. The Distant Finale also features people who have been modified to be able to insert and remove information packets from their heads, which includes arriving speaking one language and replacing it with an English version.
 * In Harry Potter Harry can speak Parseltongue, the language of snakes. He can't tell when he's doing it, so he didn't even realize this was a special power until the second book when his friends had to explain that he'd suddenly started sputtering hisses in front of everyone.
 * In a Whose Line Is It Anyway? episode Ryan and Drew are playing 90 second alphabet. When it comes to the letter Q, Ryan goes "Que?". It's made extra funny since the first line established his character's name as Garcon
 * In Final Fantasy X-2, Paine reveals out of nowhere that she can speak the Al Bhed language, something the Al Bhed she'd been travelling with didn't realize.
 * Happens twice on Friends, with Phoebe. One episode had her speaking with Joey's Italian grandmother (Phoebe seems as surprised about this as Joey), and in another she reveals she is fluent in French.
 * Finding Nemo: Dory claims to speak whale language. Marlin is less than impressed, until it actually gets them to Sydney. Dory also seems to know how to read English.