Here's one:
Yesterday we went out trick-or-treating; by the time we got back it was nearly nine and kids were all on sugar-highs and overtired; I'm trying vainly to get them into bath to wash off all the paint etc and then to bed.
DS (5) is not having this.
"But Mummy I haven't done my homework!"
Me 
"Never mind, it's too late now, you can do it tomorrow." (their half term starts today).
DS tries another tack: "Then can I go to the park on my bike instead?"
"No, it's too late, we're not going to the park now. Come and get in the bath."
"How about I just go by myself, and then you let me back in later?"
"No, you're not allowed on the road by yourself, it's dark, and IT'S BATH TIME."
This last cruel disappointment is too much for DS; he switches to full meltdown mode and wails: "MUMMY PLEASE, I JUST WANT A BEARD"
"Errr..why a beard? We're taking the face paint off now...."
"NO MUMMY! NOT A BEARD! A BEER! I WANT SOME BEER!"
I tell him to go ask his dad; this is probably his fault anyway.
Anyone got any more stories of arguments with DC that take this kind of bizarre turn?