I actually think Applejack's characterization would be ruined if she had some crazy quirk like Crazy Pie or Angryshy.
As the Element of Honesty, I dunno, it just feels like she's supposed to be the most stable of the ponies. She's a little stubborn, yes, but she's not supposed to fly off the handle.
In fact, the episode where Applejack is overworked and actually does start acting strange is one of my least favorite episodes precisely because I find her actions in that episode so unbelievable. I can see Pinkie Pie or Fluttershy or even Rainbow Dash losing themselves due to a lack of sleep, but Applejack's too responsible for that.
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