Double Proposal is the fourth stage in Forbidden Bride Pt II.
Battleground
The battle starts off with one Shibalien, followed shortly by Cyberhorn and Mistress Celeboodle. Shibalien continues to spawn every 13.3~26.7 seconds, while Mistress Celeboodle spawns every 20~26.7 seconds. After 26.7 seconds, the first of five Helmut Krabbes will spawn, with the other Helmut Krabbes spawning after 33.3 seconds each. The boss, Gorilliam, shows his face after 48 seconds, and another significant threat, Nimoy Bore, will spawn after 73.3 seconds.
Strategy
As all enemies in the stage are Aliens, any Anti-Alien Cats will make it much easier. Best cats to bring are Psychocat and Castaway Cat. True forms will help improve the chances of slowing/freezing enemies. Having Anti-Alien Treasures will reduce the magnification of the enemies and make your meatshields last longer.
A large stack of Castaway Cats and meatshields should be able to permafreeze all of the enemies, especially as the strongest pushers, Cyberhorn, Nimoy Bore, and Gorilliam all have a shorter range. In the case that the continuous freezes miss, a stack of Psychocats should be able to slow the enemies long enough to keep most of your units alive and allow Castaways to freeze once again.
If levels are high enough (30+ for all, 20s may work if high enough level Treasures), the easiest strategy is to just spam meatshields like Wall and Crazed Wall along with Castaway and Psychocat whenever possible. Mistress Celeboodle should provide sufficient money to upgrade wallet and build up a stack of the aforementioned cats.