6. Reba McEntire and Melissa Peterman
When they cast Peterman as the new wife to country legend-turned-TV star McEntire's ex in her 2001 eponymous TV show, Reba, little did the superstar know they'd become best friends on the show and off. A firm friendship was born that flourishes still today. In fact, TV daughter Joanna Swisher Garcia said earlier this year the whole cast remains close, seeing each other frequently and wouldn't be averse to some revival action!