说到 / 想到哪儿去了: what are you saying / imagining!
【高142】口语格式 / fixed patterns
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
说到哪儿去了 and 想到哪儿去了 are ready-made protests: you tell the other person that what they have just said or imagined is far off the mark. Literally “how far did you go in talking / thinking?”, in English “What are you saying!”, “What are you imagining!”, “Not at all!”.
You say 说到哪儿去了 when the other has misunderstood or twisted what you said (你看你，说到哪儿去了，我说的是买蛋糕的问题), and 想到哪儿去了 when they have jumped to an excessive conclusion or suspicion (你想到哪儿去了！我肯定不会跟别人说的). After the exclamation comes almost always the real explanation, what you meant.
It is said with a smile or a little irritation: it defuses a misunderstanding more than it picks a quarrel. The final 了 is obligatory, and it is not a question about a place: do not answer “到北京去了”. Do not confuse it with the modest formula 哪里哪里 (“you flatter me”), which answers a compliment. Register: spoken, among people who know each other.
Examples
你想到哪儿去了！我肯定不会跟别人说的。
Nǐ xiǎng dào nǎr qù le! Wǒ kěndìng bú huì gēn biérén shuō de.What are you imagining! I'd never tell anyone.
说到哪儿去了，我是夸你呢，不是笑话你。
Shuō dào nǎr qù le, wǒ shì kuā nǐ ne, bú shì xiàohua nǐ.Not at all! I'm complimenting you, not laughing at you.
你看你，说到哪儿去了，我说的是买蛋糕的问题。
Nǐ kàn nǐ, shuō dào nǎr qù le, wǒ shuō de shì mǎi dàngāo de wèntí.Come on, you've got it all wrong: I was talking about buying the cake.
你想到哪儿去了！他只是加班，不是跟别人约会。
Nǐ xiǎng dào nǎr qù le! Tā zhǐshì jiābān, bú shì gēn biérén yuēhuì.What are you imagining! He's just working overtime, he's not meeting someone else.
你说到哪儿去了，我哪敢怪你，是我自己没说清楚。
Nǐ shuō dào nǎr qù le, wǒ nǎ gǎn guài nǐ, shì wǒ zìjǐ méi shuō qīngchu.Don't be silly, how could I blame you? I just wasn't clear.
Common mistakes
✗ 你说到哪儿去？ → ✓ 你说到哪儿去了！ (the 了 closes the formula).
✗ 你想到哪儿去了吗？ → ✓ 你想到哪儿去了！ (it is an exclamation, not a question with 吗).
✗ 想到北京去了。 (as an answer) → it is a protest, not a question about a place: you answer with the real explanation.