In the UK, Van Dyke's name has become a byword for someone can't imitate an English accent successfully – the result of the American actor's woeful imitation of a Cockney chimney sweep in the film Mary Poppins.
Cf. the following usage:
"I’m a Londoner with a very neutral British accent living in the US and my (American) Siri doesn’t understand me either. I have to repeat myself numerous times and in an increasingly bad American accent to make myself understood. And since I am the Dick Van Dyke of American, this can get very tedious. Why not use British Siri, you ask? British Siri understands me perfectly, but unfortunately it has been programmed to say "I can only search for businesses, maps and traffic in the United States, and when you’re using US English’, which seems very unreasonable to me. Why can’t I search for US businesses in British English?" – A reader writing on Andrew Sullivan's blog "The Daily Dish", http://andrewsullivan.thedailybeast.com/2011/10/hogmanwhat-ctd.html