Repeat What You Just Said

Bob is talking to Alice. Alice may have a problem and be looking for inspiration to solve it; Bob engages in a long and unhelpful monologue while Alice ponders, but one of Bob's comments ignites a Eureka Moment. Alice promptly turns to Bob and says, "Wait. Repeat what you just said." Bob, bemused, repeats the very last thing he said—which is usually irrelevant. Alice impatiently retorts: "No, what did you say before that?" Bob repeats it, and it's exactly what Alice needed to hear.

Alternatively, Bob's monologue may be an attempt to hide the truth inside a long distraction (see also Bread, Eggs, Milk, Squick):

"Bob's Dad: So what'd you do with Alice? Bob: Not too much, went out for pizza, stopped at the mall, got a parking ticket, hung out at the arcade, went down to the park, same old stuff. Bob's Dad: Wait... Repeat what you just said. Bob: I went down to the park? Bob's Dad: Before that. Bob: Stopped at the mall? Bob's Dad: after that... Bob: "comma, space?""

If he can remember so clearly what it isn't, he could probably save a lot of time by remembering what it is, but that wouldn't be as interesting.

Is very much a case of Truth in Television.

Anime and Manga
"Policeman: *rushes in* Inspector Yakamura! We've finished getting all of the Ryokan employee's alibis! At the time of the crime, it seems everyone was preparing breakfast. Yakamura: Say that one more time. Policeman: Umm... At the time of the crime... Yakamura: No, before that. Policeman: The Ryokan employee's alibis... Yakamura: Before that. Policeman: In- Inspector Yakamura... Yakamura: Ah! That's it, that's it! Good work!"
 * Detective Conan:

Film
"Young Calogero: Bless me, Father, for I have sinned. It has been one month since my last confession, and these are my sins: I missed Sunday Mass twice... I lied about witnessing a murder once. I ate meat on Friday... Priest: Wait. Can you back up a bit? Young Calogero: I ate meat on Friday once? Priest: Not that one. Back up a little more. Young Calogero: About witnessing a murder? Priest: Yeah, that's the one. Do you realize what you said? Young Calogero: It was only once, Father!"
 * There's an absolutely hilarious version in A Bronx Tale. An eight year old boy from the Bronx witnesses a mob boss kill a man, but follows the code of silence by not telling the police anything. When he goes to confession, however, rather than leaving it out entirely he tries to squeeze it in between sins like missing Sunday Mass and eating meat on Friday. Naturally the priest catches on and responds with this trope. Link to full scene.

Literature
"Leonard:Oh, yes, Leshp. I made some sketches there a few years ago. Conversation continues. Eventually, a dissatisfied Vetinari leaves. Ten minutes later: Vetinari: (coming back in) You did what?"
 * Happens in the Discworld novel Jingo, when a chance remark of Leonard's plants the seed of Vetinari's grand plan, and one of his definitive crowning moments of awesome. The two are discussing an island which just rose out the see a few days ago.

Live-Action TV
"Lisbon: Where is everyone? Van Pelt: Weird, they all called in to sign out. Jane wasn't feeling well, Rigsby's got a hot date, and Cho got Kings tickets. Lisbon: Son of a-- Van Pelt: What? Lisbon: Jane doesn't get sick, Rigsby's not on a date because he's in love with you, and the Kings aren't playing tonight. Van Pelt: You know about that? Lisbon: Yeah, they're on the East Coast road trip. They're playing the Knicks tomorrow night. Van Pelt: No, I mean about Rigsby. How do you know about that? Lisbon: Everybody knows that. The attorney general knows that."
 * Full House did the second variation in the episode in which Rebecca goes bungie jumping.
 * The Mentalist:

"Suspect: When are you people gonna stop hassling me? You've got the real killer here. That dope-smoking, chain-snatching, little thug right over there. He killed her. Everybody knows it. Monk: Excuse me. Wait a minute. Hey, did you hear what he just said? Stottlemeyer: Yes, I did. I wonder why you're asking. Monk: Did you hear what he just said? Suspect: I didn't say anything. Monk: You just called that young man "a chain-snatching, dope-smoking little thug." Suspect: I was being kind. Monk: How did you know about the chain-snatching?"
 * Monk:

Theatre
"Rosemary: Darling, I don't care if you work in the mailroom, or you're Chairman of the Board, or you're President of the United States, I love you. Finch: Say that again. Rosemary: I love you. Finch: No, before that."
 * How to Succeed In Business Without Really Trying as a running gag, ending the show as an unfinished punchline:

Web Comics

 * The Order of the Stick, here.

Western Animation
"Katara: Wait, what did you just say?"
 * In Avatar: The Last Airbender, Katara first notices Aang as a potential romantic interest because of one of these: an offhand comment by Sokka had echoed a Fortune Teller's prediction of her love life.

"Vlad: I've forgiven Jack for many things: causing the accident that ruined my life, stealing you, the backwash incident- Maddie: Whoa, whoa, whoa, back up. What was that last one? Vlad: Um, causing the accident that ruined my life? Maddie: No, after that. Vlad: The backwash incident? Maddie: (Annoyed) No, in the middle! Vlad: You mean the stealing you part? Oh, Maddie, you could always see right through me! I'm just going to come out and say it! Maddie, please dump Jack and stay here!"
 * From the Danny Phantom episode "Maternal Instinct":

"Jazz: Oh, Uncle Vlad, I've runaway from home; my father's an idiot, my brother hates me, and I wanna live with you. Vlad: Wait, what was that? Jazz: I've runaway from home? Vlad: N-No, after that. Jazz: My brother hates me? Vlad: No, in the middle! Jazz: My father's an idiot? Vlad: *joyous* That's the one!"
 * And again in "Secret Weapons":

"Lois: I'm sorry Peter. I feel so foolish. It just seemed like such a good cause. Everyone in the tribe gets a share of the casino's profits. Peter: What did you just say? Lois: I'm sorry Peter. Peter: After that. Lois: I feel so foolish. Peter: After that. Lois: Casino's profits. Peter: Before that. Lois: Everyone in the tribe. Peter: Now the whole thing. Lois: Everyone in the tribe gets a share of the casino's profits. Peter: That's it! Let's go."
 * Family Guy, "The Son Also Draws"

"Lois: What exactly did they inject you with? Peter: Hepitis vaccine, some steroids, the gay gene, calcium, a vitamin B extract... Lois: What did you just say? Peter: The gay gene. I assumed that's what you meant, even though it wasn't literally the last thing I said, when you said "What did you just say?", it's just that was clearly the most ununsual."
 * Averted hilariously in another episode, Family Gay

"Paula Small: What were you saying? Brendon: Can we move the flowers? Paula Small: Before that. Brendon: This meatloaf is dry. Paula Small: Before that. Brendon: This is meatloaf? Paula Small: Before that. Brendon: This fish is dry."
 * Foster's Home for Imaginary Friends, "Dinner is Swerved."
 * Some beautiful back-tracking in episode 201 of Home Movies:

"Huey: Uncle D wants us to clean our room. Dewey: But that's a lot of work! Louie: So we thought you might have something that would do it for us! von Drake: Okay, what do I got around here? We got a karaoke simulator, Belgian cheese duster, superhero machine over here, subatomic room cleaner... Louie: What did you just say?! von Drake: The subatomic room cleaner! Ho ho, that's it, hoo! You know, if you can keep it from exploding and blowing up. Huey: No no, this! The superhero machine!"
 * Variation in Quack Pack, as the thing that's being repeated is actually the one that you'd expect should be, but the triplets only hear what they want to.

"Patrick: He really needs to get to the great beyond. SpongeBob: Patrick, say that again. Patrick: That again. SpongeBob: No, the other thing. Patrick: No, the other thing. SpongeBob: No, what you said before... Patrick: No, what you said before... SpongeBob: Never mind, I've got an idea. Patrick: Never mind, I've got an idea."
 * Played with in SpongeBob SquarePants, "Squidward the Unfriendly Ghost":

"Jeremy: *to Candace* What I like about you is..."
 * Used in Phineas and Ferb, by a (maybe purposely) obtuse Jeremy;

[they are interrupted by a giant rainforest growing underneath their picnic spot] "Jeremy: Wow, this is incredible! Candace: Um, what was that you were saying? Jeremy: I said "this is incredible!" Candace: No, before that? Jeremy: I said...."wow"!"