If Hollywood has taught us anything, it's that opposites attract, and everyone has a random. (Not that we're judging, cough cough.)
You don't need to look any further than this slideshow for proof. Behold, 18 couples, past and present, who still (still!) have us scratching our heads. Some of them work, some of them really didn't, and all of them just seem completely arbitrary. It's like waking up finding out that your single mom is dating your old science teacher, Mr. Kemper.
Chalk it up to the mysteries of chemistry. What seems good on paper may turn into a total mess, and vice versa. If Fred Armisen floats Natasha Lyonne's boat, who are we to judge?