How can you do this consistently? I don't think it is possible with universal equality.

gistfile1.scala

class Animal(val name: String) {
  override def equals(a: Any): Boolean =
    a match {
      case a: Animal if a.name == name => true
      case _ => false
    }
} 

class Cat(name: String, val color: String) extends Animal(name) {
  override def equals(a: Any): Boolean =
    a match {
      case c: Cat if super.equals(c) && c.color == color => true
      case _ => false
    }
}

val a: Animal = new Animal("Bob")
val b: Animal = new Animal("Bob")
val c: Animal = new Cat("Bob", "Orange")

a == b // true
b == a // true

a == c // true
c == a // false