While seeing stereotypical russian using "da" instead of "yes" (which is like second english word you learn after "hello") is amusing, this right here is probably a mistake. "Мальчик" usually means male kid/teen and if it's used to address adult person, it is usually to point out their immatureness or childishness. Or if some older bigger guy wants to be a creep. You were probably going for something like "паренёк". It's a diminutive form of "guy" and is normally used by older people to address young males. Not formal, but not disrespectful either.
