Follower of the Many-Faced God says:

"Response: After you play a character with the stalwart keyword from your hand, choose and stand a Stark character."

My question is, when I play the Follower or another stalwart character, can I trigger the Follower's response and choose a Stark character that's already standing as the target? Specifically, could I choose a standing Eddard Stark (TTotH) so that I could cancel the effect and draw a card?

Standing is not a cost, and it doesn't say to "choose a standing character", so I think that should work.

Entirely possible. With the templating "choose and stand a character", the targeting requirement is to choose a character, no more. The targeting requirement is *not* to choose a kneeling character, so it is entirely acceptable to choose a character that is already standing for the effect. And since in your example a Noble-crested character was chosen as the only target of a triggered effect, you can indeed cancel that triggered effect with Eddard's ability, then draw a card. That the triggered effect, if it had resolved, would've done nothing is of no consequence here.

Great, that's what I was hoping. Thanks for the quick replies.