What did the little mountain say to the big mountain?

Q: What did the little mountain say to the big mountain?

A: Hi Cliff!

This is a riddle in the standard Q and A format. It is also a pun. The reason why this pun is funny is because because cliff is a name, and also a geological feature which is usually associated with rapid changes in elevation - such as those found in mountains.

That being said, it really isn't that funny a joke. It is Laffy Taffy level at best.