为什么我要姓李因为你在我心里
[wéi shén me wŏ yào xìng lĭ yīn wéi nĭ zài wŏ xīn lĭ]
A playful pun using the fact that 李 (Li) is both a common Chinese surname and means plum. Roughly translated as 'Why do I bear the surname Li? Because you're on my mind/plum hearted.', it conveys adoration.