“I write fantasy. The only science fiction I have written is Fahrenheit 451.”

The Twilight Zone, "The Fugitive" (1962).
The Twilight Zone

Interview with Weird Tales (24 May 2007) http://weirdtales.net/wordpress/2007/05/24/george-rr-martin-on-magic-vs-science/
Context: I think that for science fiction, fantasy, and even horror to some extent, the differences are skin-deep. I know there are elements in the field, particularly in science fiction, who feel that the differences are very profound, but I do not agree with that analysis. I think for me it is a matter of the furnishings. An elf or an alien may in some ways fulfill the same function, as a literary trope. It’s almost a matter of flavor. The ice cream can be chocolate or it can be strawberry, but it’s still ice cream. The real difference, to my mind, is between romantic fiction, which all these genres are a part of, and mimetic fiction, or naturalistic fiction.

In Joy Still Felt (1980), pp. 286-287
General sources

Ray Bradbury interview http://lists.topica.com/lists/gsn-newsday-list/read/message.html?sort=t&mid=911788456 March 23, 2005

Bradbury Talk Likely to Feature the Unexpected (1994)

In a panel about his work in Comic Con 2010. Quoted in China Miéville Takes Comic Con http://www.tor.com/blogs/2010/08/china-mieville-takes-comic-con.

Bradbury Talk Likely to Feature the Unexpected (1994)

"Rod Serling Recalls Planet of the Apes" http://twilightzonewor.fr.yuku.com/topic/7412/Rod-Serling-Recalls-Planet-of-the-Apes#.VmHyirgrLIU.
Other