Here is a grumpy cat holding a sign. Print it and put it on your desk, and you don't have to say anything to anyone anymore.

STL files provided will give you about 75 mm tall cat. Model surface looks quite spiky, but print gives you nice furry surface. No supports needed.
I printed mine 0.15 mm layers 60 mm/s PLA.

Print a cat and a sign, push the sign to hole in cats left pawn, you may have to open the hole with a drill bit or shave the shank of the sign to fit.
There is also version of cat with no hole, if you like your cat just grumpy without sign.
Both versions are available with a bottom plate for those of you who have troubles with sticking your filament to bed.
Modeled in Blender and Sculptris.

Print it, but don't expect to enjoy it. :P

This is a work of fiction. Any resemblance to other grumpy cats, living or dead, is not intended and is purely coincidential.