tā / bù / xiǎo / xīn / shuō / lòu / zuǐ / le / bǎ / shēng / rì / jīng / xǐ / gào / su / le / wǒ

他不小心说漏嘴了，把生日惊喜告诉了我。

He accidentally let it slip and told me about the birthday surprise.