The process by which people see emotionally significant images in random patterns is called pareidolia, and is well-known to psychologists. Most of us can see faces in clouds or coffee stains (though in 2008 Phil "The Bad Astronomer" Plait talked about seeing the face of Vladimir Lenin in a steam pattern while taking a shower!). Those who are devoutly religious often interpret the images as personal messages or affirmations of faith. The "Jesus tortilla" and "Virgin Mary grilled cheese sandwich" are two famous examples. A Massachusetts woman, Mary Jo Coady, recently saw an image of Jesus Christ in brownish burn residue on an iron in her daughter’s room. Coady told reporters that she and her two daughters are convinced that the image looks like Jesus, and that it is a sign that he is "listening" and reassuring the family.
Though countless people claim to positively identify holy images in their scorched foodstuffs and irons, it is worth noting that no one knows what Jesus Christ nor the Virgin Mary actually looked like. There are of course no photographic images (or even contemporaneous paintings) of these figures, so it is logically impossible to "identify" their faces without an accurate reference. What Coady and others really mean when they say the image "looks like Jesus" is that the image resembles at least some of the Roman Catholic depictions from one particular artistic tradition.