how does the main guy always get a super hot chick

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can someone please explain to me how this geeky looking guy always ends up hooking up with like the hottest chick that happens to be around at the time.....idk.....maybe he just has skillz but still...(or it could be the fact he's a doctor) ..but yah....and if someone could refresh my memorie on what his name is because i just started watching it