Noodles chatters his teeth after he has yawned - he has a very high pitched yawn! He also groans when he is relaxed and when I rub his ears! And he does dressage If he is excited he does lovely lateral movements and passage!
Axel does that too, he LOVES getting his ears rubbed, gently pulled and massaged, he'll dip his head right in and growns deeply, bliss
My Lurcher does it if very excited or stressed (when I first started leaving her in day kennels she would do it when she realised I was leaving her there, and also when I picked her up at the end of the day). So not quite as cute as your stories!
My Whippet chatters his teeth,he also does a wicked Elvis impersonation,I discovered that gently tickling his ear makes him pull his upper lip into a classic Elvis,its very,very funny and when I can get a photo of him doing it I shall post it on here-"uh-huh"!
Bella or Tom dont do that but Bella is very vocal and loves a good roo , you can a 'conversation' with her its ever so funny ! She lets you know she wants something with a big ARROOOOO !!!1 ;-)
We have had a few greys that chatter their teeth, but had one old girl who sounded like a pneumatic drill when she chattered hers!!