One of his first creations was when a woodpecker was drumming nearby. Koko's teacher signed 'Koko, listen bird.' Koko held the sign for 'bird', looked at his teacher and raised his eyebrows. With this gesture he had turned a statement into a question; then, having established that he understood, he gave the woodpecker it's gorilla-style name, 'listen bird.'
On another occasion, Koko was asked about death. The conversation went as follows:
Teacher: Where do gorillas go when they die?
Koko: Comfortable hole, bye.
Teacher: When do gorillas die?
Koko: Trouble old. And tigers.
Teacher: Don't like tigers?
Koko: Frown bad red.
Teacher: I like tigers.
Koko: Tiger nail rough.
Teacher: What animals do you like?
Koko: Gorilla love."
--The Earth, Its Wonders, Its Secrets: Intelligence in Animals (1994)