Street voices
"Who pissed in your Cheerios? Something you say to someone to comment on the fact that they seem really angry or grumpy at the moment. Yo, what's up, Max? How you doing? Yeah, what's up, John? Fucking whatever, man. Hey, what the fuck? Who pissed in your Cheerios this morning?"
What it means
You throw this at someone who's being weirdly grumpy, snappy, or sour for no clear reason. It's cheeky, a bit rude, and mostly used as banter, not a serious attack. The cereal image makes the whole thing land funnier, like their morning mood got wrecked before the day even properly started.
Usage examples
"Dude, I just asked if you wanted fries and you looked ready to fight the waiter. Who pissed in your Cheerios this morning?"
"You have been snapping all morning, who pissed in your cheerios?"
"One grumpy reply and I asked him who pissed in his cheerios."
"You don't have to bite my head off, mate. Who pissed in your Cheerios?"
"I said good morning and she sighed at me like I'd ruined her life. Who pissed in her Cheerios?"
Where it comes from
An American quip, also said with cornflakes, asking what soured someone's morning. The breakfast-cereal image keeps it playful rather than hostile, as if their whole mood got sabotaged before they even left the kitchen.
Editors of this term
Unexpected Giggle Hunter Official watcher of this expression
Tell me, what have you got for me?