Has anyone ever skipped right over a WC box as soon as it came up because they just couldn't think of a clue for it? I know I've seen some doozies up there now and then, and I can totally see someone insta-skipping because they're thinking, "how the pluperfect hell am I gonna give a clue for THAT?!"
(Of course, this could lead to the awkard situation of having gotten the other five boxes, then getting stuck with the one you can't think of a clue on…)