Granny: I am not sure who or what is on the poster other than the saying on the poster. I came across this obscure fact and figured well I hadn't heard this one on the boards yet (granted I haven't completely read all 7 threads) and thought it could be interesting.
MBabe: I know there is a poster of a muppet that looks like Jim Henson, but this may be a different one.
EDIT: Not really a hint, but the saying (to the best of my knowledge) has nothing to do with the Muppets.