Looks like typical double exposure. Here are some other examples of 'friends':
http://nicnichols.com/FourCornersDark/wp...80001a.jpg
http://nicnichols.com/FourCornersDark/wp...0/meat.jpg
http://abduzeedo.com/30-interesting-light-leak-shots
http://www.flickr.com/photos/66226693@N00/3631634896
http://www.flickr.com/photos/myredreng/4399277282/
http://nicnichols.com/FourCornersDark/wp...80001a.jpg
http://nicnichols.com/FourCornersDark/wp...0/meat.jpg
http://abduzeedo.com/30-interesting-light-leak-shots
http://www.flickr.com/photos/66226693@N00/3631634896
http://www.flickr.com/photos/myredreng/4399277282/