Q: Can a leopard hide anywhere he wants? A: No, he is always spotted!\nWhat do you think is the punchline of the above joke?
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: