I was at a Japanese high school and I was playing basketball with some of the kids out in the yard. For some reason no one found it odd that a white guy in his mid 20s was there, but they all thought I didn't understand Japanese. Later we went inside to watch a video for class and had to sit cross-legged on the floor, I accidentally bumped shoulders with one of the male students and without thinking I said "ah, suman" and suddenly they all started crowding around me like "UWAA SUGOI GAIJIN-SAN HONTOU NI NIHONGO SHABERERU?".