This is totally a wishlist bug.  Some day I will wonder what possessed me
to file it.  ;-)

It would be nice if "sticky" windows really were sticky--that is,
penguins would stick to them instead of falling off.  I suppose the usual
images inverted for walking along the bottom edges of windows would be
fine.  Physics be damned--we already have penguins skating _up_ the edges
of windows.  IIRC there's some kind of rope thingy in Pingus (?) which
features penguins going hand-over-hand along a horizontal line above them.
Maybe that's not Pingus, but a similar game...

Another possibility would be an option that makes the "sticky" attribute
behave more like "flypaper"--i.e. when a penguin touches a sticky window,
it stops where it is until the window goes away or stops being sticky,
or the penguin meets one of the other horrible penguin ends.

Still another possibility makes "sticky" become "magnetic" or "vacuum",
sucking up penguins if they merely stray near the window.  Probably best
used only with "flypaper".