Ha! This is one of my favorites! Ironic, isn't it, that my name is Stork and I love cats?! (My cats were not too happy to take that last name when I married my husband!)
Here, for your enjoyment, is a sorting activity (with a rather wacky theme) dealing with irregular plural forms of words (child - children; tooth - teeth, etc.) There are two category signs under which students will sort the fish cards!
Just print, laminate, and enjoy!