We are crazy, we are crazy 
We are nuts, we are nuts 
Happy little morons, happy little morons 
We are nuts, we are nuts. 

And here's a second version:

We are crazy, we are crazy, 
We are nuts, we are nuts, 
Funny little moon men, funny little moon men, 
Brrm, brrm, eek! Brrm, brrm, eek! 

(brrm = sort of car noise, and waggle finger over lips like a
baby! On "eek!" make two little horns on head with index fingers)