Lei Seng Mut? (What's Your Surname?)

Ethan carted home all his workbooks and files from school this afternoon as final year exams are starting tomorrow and students have to clear out their desks and classroom cupboards. I went through his files and found this:

My hobby is reading. You can learn a lot while reading. But you can't overdo reading, if you do, you may even forget your surname!

LOL. No prize for guessing where that comes from: we "chide" him in Cantonese whenever he is too deeply engrossed in reading to give a care to what is happening around him, "Lei seng mut doh mm tsi", meaning "you don't even know your own surname" or for greater emphasis "Lei loh dow seng mut doh mm tsi", meaning "you don't even know your dad's surname". Ah, beware of what you say to your kids. You never know how it would come back to "haunt" you!