A large wave of Wall Doges and a few Metal Doges start the stage. H. Nah and more Metal Doges will continue to spawn fairly quickly a short while later, and will continue to do so throughout the stage.
This level can be a massive pain unless you come prepared.
Items: Rich Cat, Cat CPU.
When the first Metal Doges come out, summon a Dragon, Paris, and Space Cat, along with a couple more Paris. As you accumulate more money, summon Ururun, Bahamut, and the uber.
You should have Cat CPU turned on by now to constantly summon your meat shields. This will keep the H. Nah and Metal Doges off your other units. After a while, you should have won. Take a minute to do a victory dance. This is one hellish ordeal of a level.