"Do you mean it?" and "For real?" have roughly the same meaning, which is "Is that really true?" "Wouldn't you know it!" is more of an exclamation of something that you didn't expect in a bad way. "That president turned out to be okay, wouldn't you know it!" - see http://en.wiktionary.org/wiki/wouldn%27t_you_know_it Note that "For real?" and "Wouldn't you know it!" are American English idioms.