It always seems to me that Mon Mothma, after introducing Ackbar and letting him give his plan to the assembled rebels, seems to stare at him with her mouth slightly agape in "Wow! Thats a really good puppet! I cant believe they managed to get this working like that!!!" fashion.
(It also could be a look of "Oh shit..! They're really going with this..? Wow. What is this...? The Muppet show...?" kinda look too.)