Related:

• He's a few cards short of a deck.
• His puzzle is missing a few pieces.
• Source code is missing a few lines.
• A few tiles missing from his space shuttle.
• Missing a few buttons on his remote control.
• Get well cards have become so humorous that if you don't get sick you're missing half the fun.
  WILSON...
• Cards? Luxury! I was at the smithy 18 hours a day forging gears for my analytical engine, Ada working her fingers to the bone assembling them on shafts.
  I used to dream of the day when I would finally get it all put together so that I could finally play 'Wumpus'....
• Changing gears, here.
• Yup, you're losing your marbles. (on a statistical problem involving marbles in a jar)