Seriously? OMG! WTF?

Mackenzie Phillips/Instagram

Valerie Bertinelli and Mackenzie Phillips started playing sisters on One Day at a Time over 45 years ago. And even though all of that time has passed, the two actresses are still as close as they were back then.

So what brought them together? They came to celebrate the man who made them sisters, 100th birthday.

That special, which also includes a Facts of Life Reunion, will air later this year on ABC.