See you later, alligator!

'See you later, alligator!' is something parents and grandparents say to little kids. The response from the child is, "After while, crocodile!"

Example:
-See you later, alligator!
-After while, crocodile!

Hold your horses!

'Hold your horses!' is a way of telling someone not to get too excited about something because it isn't sure if it will happen or not.

Example:
-We're putting an offer down on the house.
-(child): For real?! I'll get my own room and my own bathroom! And...
-Hold your horses, sweetie. They haven't accepted our offer yet.