In high school, the AP/IB biology teacher kept his thorny dragon in a 55 gallon terrarium in the back of the class room. I think the teacher was really smart for picking that guy as a classroom pet.
The way the thorny dragon moves is a sort of oscillating swagger, and it's entire body is covered in spines that look just like huge blackberry thorns. And if some ants were put in the tank, the thorny dragon would convert from being a particularly sharp rock, into the master predator. Just lightning fast, you'd miss all his movements if you blinked.
Not very cuddly, but a beautiful animal, and a nice conversation piece.