I still say poor Bailey went mad from hearing Balok's obnoxious laugh at every little instance, day in and day out, week after week, month following month until they amounted to years. When Kirk finally returns to retrieve the former navigator, they find the Fesarius damaged almost beyond repair, more than half the domes cracked or outright shattered. When a rescue team beams aboard the vessel, they find Bailey crouched and trembling in a corner, giggling and drooling.
Bailey glares at the landing party with a manic grin. "We were wrong! It was a double bluff! It wasn't a puppet after all! That was the real Balok! The child-like alien? That was the fake. I mean, how could something that laughed like that at every least provocation be real? No, the genuine Balok sat there in silence, observing, scrutinizing, seeing if we would fall for the ruse. But I saw through the farce! I proved it by tearing the stuffing from that snaggle toothed doll. Funny, I expected foam rubber padding over a hydraulically driven armature, but Balok seems to have employed some sort of gel strand pneumatic construction with fluid dynamics. A bit volatile however as it began to slowly dissolve once the interior mechanisms were exposed to the atmosphere. Released quite a bit of noxious fumes as well..."