Q: Can a leopard hide anywhere he wants?
A: No, he is always spotted!

Explanation:  If you have ever seen a leopard, you will know that leopards have spots. Spots are the round marks that a leopard has on its fur.

Spot can also be used as a verb.  To spot something means to find it or notice it while looking for it- I spotted a squirrel in the tree.

This joke is funny because it plays with the word spot.  A leopard is spotted (adjective) because it has spots; a leopard is spotted (verb) when you see it.

This is from Rudyard Kipling‘s Just So Stories about How the Leopard Got His Spots: