That's the difference between irony and sarcasm. Irony can be spontaneous, while sarcasm requires volition. You have to create sarcasm.
Christopher MooreThat's the scary thing about hope," she said. "If you let it go too long it turns into faith.
Christopher MooreWhat is your name?" asked Lear. Caius," said Kent. And whence do you hail?" From Bonking, sire." Well, yes, lad, as do we all," said Lear, "but from what town?
Christopher Moore