Why Moses and Elijah?

Matthew 17:2-3(NKJV)

2and He was transfigured before them. His face shone like the sun, and His clothes became as white as the light. 

3And behold, Moses and Elijah appeared to them, talking with Him. 

When I read this today it made me wonder, why Moses and Elijah? 

Nothing wrong with them.  Great choices.  I just wonder if there was any significance in God choosing those two out of all the great people in the Old Testament?

Think of it.  God could have chosen Abraham, Joseph, Isaiah, Daniel, or many others.  He chose Moses and Elijah.  Might make an interesting study to compare the two and see if there is any significance.

Then again maybe it is just another example of God having a little fun and just checking to see if I was really paying attention.  :)