a. A few clowns short of a circus.
b. A few fries short of a Happy Meal.
c. An experiment in Artificial Stupidity.
d. A few beers short of a six-pack.
e. Dumber than a box of hair.
f. A few peas short of a casserole.
h. The wheel's spinning, but the hamster's dead.
i. All foam, no beer.
j. The cheese slid off her cracker.
k. An intellect rivaled only by garden tools.
l. As smart as bait.
m. Elevator doesn't go all the way to the top floor.
n. His belt doesn't go through all the loops.
o. If she had another brain, it would be lonely.
p. No grain in the silo.
q. Proof that evolution CAN go in reverse.
r. Receiver is off the hook.
s. Skylight leaks a little.
t. Slinky's kinked.
u. Surfing in Nebraska.
v. Too much yardage between the goal posts.