The sarcastic interjection in your (or my, her, his, etc.) dreams is familiar in everyday spoken English, but the earliest evidence our editors have found comes from a Usenet post in 1986.

We suspect that it may have been used earlier than that; can you help us prove it? Popular culture such as film and television might be a good place to start.

Here is our entry for reference:

OED editor Fiona McPherson explains this appeal below:

Posted by OED_Editor on 26 September 2012 20.01
Comments: 19