Naughty Act 1
Nibble off the tastiest parts of the (romaine) lettuce and scatter the remains everywhere on the floor. Kick around or sit on the remains.
Naughty Act 2
Pull the lining out from under the litter box, rip it all up to make a fearsome mess.
Jump on top of the treats box which is on top of the cage.
But...see...they are so fluffy and cute that it is impossible to get angry with them. Scold them and they will just look at you with an innocent "what's wrong?" face. Or run off, kicking their heels joyfully at you.
Bunny owners are slaves :P