Two generations of Joffrey Ballet. Denise Jackson began as an apprentice in 1968 and soon became a principal dancer. When she retired, New York City declared Denise Jackson Day. Ashley Wheater joined the company in 1985 and was named artistic director in 2007. They’re both overdue for a ticker-tape parade and both on the show this week to tell us about rehearsals, Robert Joffrey and a 1956 station wagon.