Things the Roomba has eaten:

a corner of the black satin sheet that's getting retired because my nasty cracked heels have shredded it
a plastic cat spring
a different plastic cat spring
a short colored pencil
a catnip rat
the tassel on the corner of Escape Calico's cardboard scratchy-pad
a corner of the good cotton sheet, several times
a lot of long hair (both Alex and I are longhairs)
several pieces of paper
half a blueberry


Things the Roomba has mistaken for a cliff:

a corner of the black satin sheet it tried to eat
the black bath mat
to be strictly fair, the heating vent on the floor of the main bedroom is a cliff, but it's a safe one