Is my tortoise "Spike" crazy. He climbs on top of his cave and jumps off the top over the opening. Is this normal? My kids think it is funny. They say he is a ninja turtle.
If I remember correctly from your intro post, Spike is a Russian.
Russians roam huge areas in nature and in captivity are known for there enthusiasm to explore,dig, climb and jump or fall off just about anything.
They can even climb corners of tanks.
Just be careful he doesn't flip or fall into water that he could drown in or get stuck flipped under a basking light that would bake him to death.
Yes, it's normal.
Make sure he can't end up on his back in water or under the basking lamp. The former can result in drowning and the latter in death through dehydration. If he persistently ends up on his back, you may have to make some modifications so that he can be safer.