Crush fetish is a sexual desire to crush small creatures such as insects, mammals and possibly reptiles. This is extremely popular amongst the foot fetish market as the feet are the most common crushing tool, and as such the foot (which can be covered by any kind of shoe though generally high-heels are preferred, as are sizes 9 and up) is often idolised in crush erotica such as magazines (with publications including Squish! and In Step), audio tapes and crush films.
Of course, the practice of crushing animals is frowned upon by animal rights activists, and as such legislation has been passed to forbid the practice. However, being such an underground activity makes it harder to control circulation of media catering to crush freaks (harder to control than, say, child pornography). Therefore (and also because not all crush freaks want to see living beings die), other items such as food and plush toys are occasionally crushed instead.
The desire is much like that of Vorarephilia, except with the desire to crush and be crushed. It plays into both the desire to dominate and to squirm and writhe helplessly under the dominator, both of which are traits quite closely linked with S&M fetishism. The attraction can also be traced back to childhood, when children are towered over by looming domineering adults and kids begin to fantasize of becoming gigantic.
See also