You have no idea of what they've been through to entertain you..

 Dolphin captivity. You have no idea of what they've been through to entertain you for a short period of time. They've survived the violent capture from the ocean, got along with their tank mates, often bullies and attend long and inhumane training sessions just to learn how to play ball. They are voiceless, but we aren't, it is our duty to stand up for them against their cruelty. When they do so, it is not pretty : therefore orcas have been known to kill or attempt to murder their trainers after training sessions.
Don't let their smile fool you.