Lol, guandong enterprises sounds a bit iffy they wouldn't know who was who. I can imagine Guandong Snr bashing his number one son with the mug. "wight wally you haff made of us all".
Prbaly not a mistake but a clever marketing ploy.
When asked about whether the mug was a deliberate mistake, a company director said in an email: “Thank you for your esteemed interest. The cups are printed exactly as on the web screen and will stay as that. Many people are delighted in buying for gifts and family occasions and NOVELTY.”