- Bak Chang VS Tokusa
- Bak enjoys covert photography (but only when photographing Lenalee) and sneaking around headquarters. He likes Lenalee, the space between the sealed doors, studying, Won, and his own face. He dislikes snakes, unreasonable violence, hives, and Lvellie. 
- For tells Allen that a person once got lost in the Asian Branch for a week and nearly starved. Bak is undoubtedly this person, as he jumps and quietly scoffs at the comment.
- Bak is sometimes portrayed in a frog costume
- For refers to him as Baka-Bak (Idiot-Bak)
- Bak chronologically first appeared in the novel, then in the manga and finally in the anime.
- Though Chinese, Bak's last name - Chang - sounds similar to the Japanese honorific - -chan - used for name diminution. Because of this, Komui sometimes teases Bak by calling him either Bak-chan or Bak Chang-chan (Baky in the manga) instead of Bak Chang.
- Bak breaks out in hives when embarrassed or excited (As shown when Allen accidentally bumps into him and causes him to drop all of his secret photos of Lenalee).