The Drummer's Ghost

At the Haunted Fair, have 3 Ghost moles on the board at once while in FEVER. Bonk the Drummer when he shows up.
How to find it, step by step
- Unlock and start HAUNTED FAIR (win SUNNY FAIRGROUND first).
- Draft the Ghost mole and level it so Ghost moles keep appearing.
- Reach FEVER momentum with 3 Ghost moles visible on the board at the same time.
- The Drummer's ghost appears once in that run: BONK it in any way.
Reward
Hidden achievement "Fired".
Tips
In-game hint
Someone still keeps the beat at the Haunted Fair...