How to play against hippo and cow?

Against the Hippo there are many ways to play but I always find it easier to put a third pawn in the center, generally c4, which will assist in smashing open the center. What they want to do is lock the center and trade their knights off for your bishops. The Hippo is a slow opening so if your bishops are not going to have anywhere to retreat, before you put them on d3 or e3 it's OK to play h3/a3 to prevent annoying knight attacks like Ng4/Nb4.

Against the Cow, when there's a knight on g6 or b6 a common idea is to launch the h-pawn or a-pawn to kick it, you can do this quite early in the game. If they play say h5 to stop this that will weaken the knight. Usually if you trade one of those knights they keep a solid pawn structure, if they play h5 then a trade on g6 will result in a weak mess.