The 7 Trickiest Love Triangles on Grey's Anatomy

Callie and Mark's relationship is both simple and complex in equal measure. They're not in love with each other; they just love having sex with each other. They're on-call room buddies. Simple. Where it starts to get tricky is when Arizona enters the picture. All this time, Callie uses Mark to try and reconcile her newfound feelings towards women (which is fine by Mark). However, Arizona comes along, and Callie is even more confused than before. Oh, and as if things weren't confusing enough, Mark gets Callie pregnant, making them one, big, happy Grey's family!