Mary is definitely more stoic than Dean and Jack, though.
I think of Dean chewing his food messily with his mouth open, often "acting out" for Mary and Sam's benefit. I can't think of the exact episode, but I know in season 12, he eats in an exaggerated way in front of Mary and Sam, smiling cheekily like it's some private joke.
Here's an example from 15x06 when he shuffles in and pours cereal into his mouth, amping up the "oafish, childish brother" routine:
15x06 via @spnscripthunt
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Dean and Jack both tend to "act out," doing childish things...often for show, for the benefit of others, or to cover up some serious personal hurts.
I think about how Jack was shown blowing a big bubblegum bubble and amping up his charm to cover up how uncomfortable he feels being back in his childhood home and lying about Billie's plan:
15x12 via @spnscripthunt
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15x13 via @spnscripthunt
Like how Cal @soullessjack pointed out, some of Jack's fun-loving stuff (toys-and-social media and matching ties) is an at least partial performance in Gimme Shelter. There’s a good chance it’s a front in Galaxy Brain too (above)
Blowing bubbles and acting lighthearted is a cover for his own morose mood and suicidal plan with Billie.
Jack can be a silly character, but it's worth remembering that he's often potentially engaging in motivated "lightheartedness."
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Mary has a silly side, definitely, but she feels more wry / sarcastic on the whole. She's more confident, more aloof.
She's so mean on the outside sometimes, lol, and I love her so much.
I think Mary would definitely be a practical joker, but she's not as out-and-out silly or childish, and she seems distinctly less particular than Dean:
14x18 via @spnscripthunt









