Koko is indeed probably the most accomplished signing gorilla. Granted, Koko doesn't officially speak in American Sign Language any more, and I think Koko has created her own dialect. What this really means is, sometimes Koko says things that don't make any sense, and it looks vaguely like sign language. If you have GBH Select, not GBH2, then you can sometimes see Koko specials on, where they have translations of her sign language. This usually consists of a gorilla humping a woman while it shows subtitles like "Koko-shame-bad-food" and other phrases that would make total sense if you only knew Koko's dialect of sign language. However, what makes Koko truly great is the pet cat that she has (<insert monkey and pussy cat related obscene joke here>), and the occasional gigantic poster sized:

Koko-Love-You.

As a classroom full of students sign at the overeducated primate. This is what public television is all about.