A brown waldo is a bowel movement left in a strategic location that makes it hard to find. The more specific davenport (popularized by pro football player Najeh Davenport) would qualify, but a brown waldo may be dropped anywhere - not just in a closet hamper. You'll smell it before you see it!
This Christmas party sucks - I'm gonna go leave a brown waldo in their guest room.
<3 days later>
Dude ... where's the brown waldo? I can totally smell it!