Examples:

• But how come i was getting better without the medicine?
• And if that's so, how come you remember so clearly?
• Hey, how come you never introduced us to your wife?
• Yeah, but how come she didn't come to me?
• Hey, how come you want to use the phone already?
• Well, then how come he and Tanner showed up there today?
• If not, how come he would risk his life to save me?
• Then how come we've never heard about it before?
• Zezé, how come you know so much about the Zoo?
• Well, then how come his face is on the bottle?