Conversation so far:
When was Richard Christy on the Howard Stern show?
After Richard Christy obtained the number to reach the show's answering machine from the Internet, he began to submit comical voicemail messages in 1999.
Were the voicemails submitted by Richard Christy supposed to be voicemails he left for Howard Stern?
Richard Christy began to submit comical voicemail messages in 1999, that were played frequently on the air.

Question: Did he ever appear in person has a guest?
Self-contained rewrite: Did Richard Christy ever appear in person as a guest on the Howard Stern show?