Applying slime to a block that has a silverfish in them should make the silverfish jump out (it's currently not possible to put slime on such a block, which is odd).
Breaking a stone with a silverfish in it should drop the stone block (currently drops nothing)
Using silk touch should drop a regular stone and a silverfish egg
Right-clicking a stone with a silverfish egg should put the silverfish egg into the stone. If there's slime on the block, the slime should fall off before you put the egg in (since there is no mossy stone with a silverfish in it in the game)
Should it be possible to breed silverfish? They don't reproduce in the game at the moment... hm...
You have a cool idea? Write a comment!