Commencement (Episode 422)
First Aired: Wednesday, 7th May, 2003
Teleplay: Aaron Sorkin
Director: Alex Graves

Not a Josh and Donna scene, but some very interesting insight into Donna's understanding (and Amy's lack thereof) of what makes Josh tick.

You Have To Get Josh
Josh's Office. Amy and Donna have a somewhat awkward conversation about someone they have in common.

AMY: I understand why Josh may have been offended by what I said, even though it was misinterpreted. What I don't understand is, both times we've spoken about it, it seemed like you were, too.
DONNA: No. (she shakes her head and smiles) I understood what you were saying. Josh worked for Hoynes for a long time, there was a reason--
AMY: He left him.
DONNA: And if you think that was easy, you're crazy. Josh doesn't leave people.
AMY: I get that he was close to Hoynes, what I don't get is--
DONNA: (perhaps a little too firmly, and therefore tellingly) You have to get Josh.
(Amy stares at Donna, the wheels very clearly starting to turn in her head)

Again, not a Josh and Donna scene, but this was almost better ...

Are You In Love With Josh?
Josh's Office / Bullpen. Galvanised by several beers, Amy asks Donna the $64,000 question.

DONNA: His sister died in a fire while she was babysitting him. She tried to put it out, he ran outside. He went off campaigning, his father died. He wakes up in the hospital and discovers the President's been shot. He goes through every day worried that somebody he likes is going to die and it's going to be his fault. What do you think makes him walk so fast? (Donna goes into the Bullpen and continues speaking, while Amy sits and stares at her empty beer bottles as if they've just unlocked the secrets to the universe. Which, in a way, they have.) Anyway, when you looked at the list of replacements and said "That's a windfall," what he heard was, "Thank you, Josh, you did it again--more for us."
AMY: You said you have to "get" Josh?
DONNA: Yeah ... that was ... (almost anxiously, she begins to flips through a little red book, and hesitates before she continues to speak) ... I didn't mean to say that you don't ... get him.
AMY: (flatly) Are you in love with Josh?
(Donna's face goes blank as she stares down at the book for several seconds, then slams it shut)

Many thanks to The West Wing Collection for the wonderful screencaps!