What a marvelous job you've got! I haven't seen the episode either (that's no
obstacle to venturing an opinion ;-), but it sounds like variations on wet
and/or muddy feet. As Rohit pointed out, Grauman's is famous for their hand
and foot impressions in cement from stars, even canines. The Timmy reference
is probably to the old Lassie show, where a collie is perpetually performing
amazing and daring feats, often rescuing little Timmy. I don't recall a
"Timmy's fallen into the well" episode, but that wouldn't be a surprise. And,
of course, the dog's paws (at least) would get wet in such a rescue. Doesn't
the Mad About You dog look somewhat collie-like? I so wouldn't be surprised if
Lassie has a pawprint block at the Chinese theater.
Hope that helps.
"I think people tend to forget that trees are living creatures. They're sort
of like dogs. Huge, quiet, motionless dogs, with bark instead of fur."