You could suppose that cacti of the same type look similar. They will have the same color patterns and spines, but will most likely be shaped differently.
http://www.ent.iastate.edu/images/orthoptera/0189.5redleggedghopper.jpg There you go. Put it in your search box up there where it says; "http://wiki.answers.com"
No, all whales do not look the same. There is the blue whale (the largest living mammal), there is a narwhal (a whale with a bone sticking out of its "nose" that looks like a horn. There are many...