阿斗 is the childhood nickname of Liu Shan (
刘禅, 207-271), son of Liu Bei and second emperor of Shu Han. Despite being supported by the brilliant strategist Zhuge Liang (
诸葛亮), he was famously inept and surrendered to Wei in 263. After capture, when asked if he missed Shu, he replied
此间乐,不思蜀也 ('I'm having fun here, I don't miss Shu'), giving Chinese another famous idiom
乐不思蜀. His name became a byword for the weakling no mentor can rescue.