Old cartoon about multiplying yellow bricks that invade a castle? What was it?

some evil guy wants to invade a castle by creating yellow bricks that multiply and lay on top of everything in their path. the bricks proceed to the castle and the animals try everything to stop it. at one point a big lazy bear gets trapped underneath. Ultimately one of their friends goes to a laboratory in the castle and creates a mixture in a dropper. the liquid then makes the bricks recede.