Lil' Miss Badass

Coworker: *walks through office door*
Eliza: *stands cross-armed in front of door* "I'm locking you in! You can't get out!" *evil laughter*
Coworker: *fails to notice the hugely threatening small child and wanders back to kitchen area*
Me: "Careful Eliza, [coworker] is way tougher than you."
Eliza: *puffs up* "I am seven years old and you don't MESS wiff sevens-years-olds!"
Me: *uncontrollable laughter*
Eliza: *increases puffitude* "You're messing wiff me!"
Me: "No, I'm dying of laughter. I'm not messing with you, I'm laughing my ass off at you."
Eliza: *hmmph!*

Office phrase-of-day is now "I'm just sayin', don't be messing with any seven-years-olds!"