Oh noes, a spooky shadow at the window!

which appears to be dancing, but no matter.

Scooby checks outside to see what it is, but when he gets there…

…the shadow isn’t on the window at all, and is now in front of the door?

…and the shadow is allegedly coming from a chipmunk, which is: 

A. Really funny to imagine dancing side-to-side like the shadow was

B. Not tall enough to cast a shadow on the window

C. Physically unable to cast the shape of shadow they saw

D. Requiring a perfect rising/setting position of the moon to even cast its current shadow, rendered impossible by the amount of nighttime in the episode before and after this scene

But other than that, this sequence makes perfect sense.

…and then when Scooby goes up to the chipmunk 5 seconds later, the shadow’s entirely gone, because the animators themselves have the attention span of chipmunks.