Simple Vows.

Derek: I wanna be with you forever, and you wanna be with me forever. In order to do that we need to make vows. A commitment. A contract. Give me a piece of paper.

Meredith: I don't! I... I... I don't. I have post its!
Derek: (takes the post its and a pen) Ok. What do we wanna promise each other?
Meredith: That you'll love me... even when you hate me.
Derek: To love each other, even when we hate each other. (writes it down) No running. Ever! (Mer smiles and comes and sits in front of him) Nobody walks out. No matter what happens.
Meredith: No running.
Derek: (writes it down) What else?
Meredith: That we'll take care of each other, even when we're old, and smelly, and senile. And... if I get Alzheimer's and forget you...
Derek: I will remind you who I am, every day. To take care when old, senile, and smelly (writes it down) This is forever. (signs it) Sign.

Meredith: This is our wedding. A post it? (smiles)
Derek: Mhmmm. If you sign it.
Meredith: (signs it, and hands it back. Has tears in her eyes) Now what?
Derek: Now I kiss the bride. (They kiss)
Meredith: (smiling) Married.

Derek: (smiling) Married. (sticks their post it in Mer's locker) You see that? (Mer nods and smiles) Plenty of time.