- Infinite Hippoes spawn after 1.33 seconds40f, delay 2~16.67 seconds60f~500f.
- 3 Metal Hippoes spawn after 6.67 seconds200f, delay 2~4 seconds60f~120f.
- Infinite Heavenly Hippoes spawn after 23.33 seconds700f, delay 6~16.67 seconds180f~500f.
- Infinite Heavenly Hippoes spawn after 24 seconds720f, delay 20~33.33 seconds600f~1,000f.
- When the base reaches 99% HP:
Once the boss appears, have as many critical hitters out, as Sir Metal Seal is a very tough enemy and often takes a lot of Critical Hits to take out. The enemy base will continuously spawn Super Metal Hippoes, so take care of some of the enemies quickly so you won't be swarmed. Having a Wave Attack cat like Crazed Gross Cat to help take out the Hippoes hiding behind the Metal enemies as well. Having Space Cat and/or Crazed Whale Cat in your lineup is a must. It is also advised to get Fish Cat's True Form, Island Cat, before trying this stage. If you happen to have Catornado, this stage will be a lot easier.
Generally, any Uber with a special ability against Metal enemies and/or can do Critical Hits with a decent chance, will be good here. Listed below are more specified examples of good Ubers to use in this stage.
- Marauder Cat: Just like most other stages full of Metal enemies, Marauder Cat make this stage a joke as long as he is in his Evolved Form or higher.
- Hayabusa: An even better option, can destroy most if not all of the Metal enemies in this stage with his powerful, Long Distance strikes.
- Graveflower Verbena: Another critical-hitting Uber, her Multi-Hits increase her chance of doing a Critical Hit on the Metal enemies here.
- Sakura Sonic: Great crowd-control for all the Metal enemies here and has a chance to do a Critical Hit.
Cat Line-up: Island Cat, C. Whale, Space, Rope Jump (Optional but very helpful)
Start the level. The first few Hippoes have slow movement, so there is time to stall. It doesn't get bad until the Heavenly Hippoes spawn. Spam Space Cat, Island, and C. Whale, along with meatshields. There is plenty of time to get Space Cats and other critical cats.
Once the boss is spawned, do not stop spamming. If your meatshields are dying quickly, don't spawn too many expensive units. Super Metal Hippoe moves much faster, so let him get close to the base, then spam Island/C. Whale. Hopefully, he should be defeated. Then keep trying to beat Sir Metal Seal, and win the level!