Here are some punny puns:
-I wondered why the baseball was getting bigger. Then it hit me.
-Did you hear about the guy whose whole left side was cut off? He's all right now.
-Show me a piano falling down a mineshaft and I'll show you A-flat minor.
-Time flies like an arrow. Fruit flies like a banana.
- A bicycle can't stand on its own because it is two-tired.
