class Duck {
    quack() { println "I am a Duck" }
}

class Frog {
    quack() { println "I am a Frog" }
}

quackers = [ new Duck(), new Frog() ]
for (q in quackers) {
    q.quack()
}

• Objects are polymorphic without being related by a common base class or interface.
  • If it walks like a duck, and talks like a duck …
    • Then it is a duck!