Of all the legacies of the era of the sixties, three colorful, not to say garrulous, "personalities" that emerged from the early days of artificial intelligence research are worth mentioning:
ELIZA, the Rogerian psychotherapist;
PARRY, the paranoid; and (as part of a younger generation)
RACTER, the "artificially insane" raconteur.
All three of these "characters" are natural language processing systems that can "converse" with human beings (or with one another) in English. That is, when presented with sentences in English as their input, they produce other grammatical sentences as their output, which sometimes manages to give the flavor of a conversation.
I'm tired of seeing the 'ooh, look at this conversation with X bot online', so here's the definitive link: one classic bot converses with another.
Also, Racter's poetry at the end should be read with a grain of salt: this link says that most of it could not have been written by the program!