Because Chinese and western cultures are different, it is a joke caused by the word "convenience"

Peter (American) and Xiao Wang are chatting in the park. Suddenly, Xiao Wang was a little embarrassed. Peter asked, "What's the matter with you?"

Xiao Wang said shyly, "I want to be convenient." Peter didn't understand. Only when Wang went to the public toilet did he know that "convenience" meant going to the toilet.

After a while, Peter asked Xiao Wang, "When will you come to America and I'll show you around?"

Xiao Wang replied, "I want to go at your convenience." Pete; ……