Nicole Kidman and Jimmy Fallon are both great actors, yet this most of the early portion of this hilarious Tonight Show video is not acting and provides some fantastic examples of body language.
Near-Microexpression of fear displayed (mouth and eyes) by Nicole Kidman
She knows what she's about to say, but Jimmy doesn't ..... yet
A Sincere Smile & Blushing
The vast majority of the time, a sincere smile does not also have blushing clustered with it, yet blushing - if it's sincere - always is accompanied by a sincere smile (although it may be partially suppressed).
Jimmy puts his hands up and backs away - both of which are common signals of true disbelief and emotionally processing an event or sudden realization. Although many times it's seen in the context of negative emotion, and Fallon IS significantly embarrassed - this is primarily a scenario of self-deprecating humor.
2:30 - 2:33, 2:35 - 2:43, 2:46 - 2:47
Sudden facial covering (in whole or in part) is seen during moments of emotional processing. Fallon can't believe how he blew this chance to date Nicole Kidman and he's trying to wrap his emotions around what he was blind to years ago.
Sudden looking & turning away with the head, neck (and also with his entire body as he walks off stage shortly thereafter - even thought this was partially melodrama) also signals disbelief and emotional processing
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