At the start of the level, many Owlbrows will appear. If you go REALLY slowly, a Mooth will appear before you can hit the castle. When the enemy base is hit, Teacher Bun Bun will come out. Mooths will also spawn constantly after the wave of Owlbrows dies.
Cat Line Up: Mohawk Cat, Eraser Cat, Crazed Macho, Crazed Whale, Jamiera, Paris Cat, Bahamut Cat, Dragon Cat, Crazed UFO and The Flying Cat. Higher levels are preferred.
Save some money and spawn Dragon, Jamiera and Crazed Whale when the Owlbrows come near your base. Do not exaggerate spamming them. If by the base your Worker Cat is level 6 or higher and it is full, you did a good job. As the base gets hit, Teacher Bun Bun exits it. Some moments before that, activate the Cat Cannon to knock back Teacher Bun Bun to give the player more time. At the SAME moment, start spawning all of your cats. Cat CPU might be of help here, the spamming needs to be constant. Mooths will spawn with Teacher Bun Bun, to provide the player with money. Kill Teacher Bun Bun and the level will be free. Go for that base and finish the level.
Strategy 2 (Ft. Tesalan Pasalan)
Cat Line Up: Macho/Mohawk, Wall/Eraser, Samba (another spammer if wanted) Paris/Dragon, (or both), Delinquent Cat, Crazed Bahamut, Tesalan Pasalan. (Other anti floatings can help)
This is doable without any crazed cats. When the Owlbrows get close to your base start spamming Wall/Eraser and stack Dragon or Paris. Once your money is high deploy Crazed Bahamut and Tesalan Pasalan and spam everything. The Mooths have longer range than Teacher Bun Bun so they won't be hit by Tesalan Pasalan. Once Teacher Bun Bun is dead, defeating the base is easy. Don't stop spamming as the Mooths may kill your big hitters if they are unprotected.