(to TRINCULO) Thou liest, thou jesting monkey, thou! I would my valiant master would destroy thee. I do not lie. " (The Tempest, Act 3, Scene 2)
Caliban calls Ariel "a jesting monkey" and a liar, who is in turn, speaking as Trínculo. Ariel is imitating Trínculo´s voice and is invisible, thus the confussion. It is worth mentioning that "jester" means fool.
Because all though he knows his sister is dead, he can still hear knocking and scratching sounds coming from her coffin. She's dead, but comes back to life to haunt him causing his madness to grow stronger.
