萌得无药可救呆得病入膏肓
[méng dé wú yào kĕ jiù dāi dé bìng rù gāo huāng]
This nickname translates to 'So Adorably Innocent and Silly There’s No Cure', expressing that someone is irresistibly cute but also very silly or naïve, to the extent that it can't be fixed. It suggests a character that is endearing but perhaps overly innocent or absent-minded.