Eureka: just realized: a major reason that - if forced to choose - Jenna and GOB are my favorite characters in their respective shows: = their shared trait of reliably giving socially incorrect responses - even (maybe especially) in fleeting, wordless reaction shots - to every thing that ever happens around them - including their own statements and actions.  Two favorite examples leap to mind:

Jenna (with wounded dignity): I never heard back about my audition for Everybody Loves Raymond. I'd wondered if you'd made a decision.
Phil Rosenthal: Yeah, 15 years ago. We went with Doris Roberts. ...But thank you for tying your headshot around a brick and throwing it through my window.
Jenna: [bashful proud half-smile, like a child who's just been praised for doing a minor task well]

(From possibly my fav episode of the entire series: model home kitchen; Lindsay is sitting at the counter on the outer side; to her right, GOB is standing, and to his right, Michael is standing inside the kitchen)
Michael: GOB, do you remember growing up with a...sister? [referring to mysterious "Nellie"]
GOB (mostly while looking directly in Lindsay's face): Sister? Uh... no, I don't. Not really... ringing any bells.
Michael: Other than Lindsay, of course.
GOB: Oh! Lindsay!!!
[GOB looks back and forth between Lindsay and Michael, looking super pleased with himself, like a dog expecting a treat]