My brother's friend's girlfriend was babysitting (I think), and took the toddler into a coffee shop where she spotted an old man.
Kid: Why doesn't your skin fit your face?
Old Man: It's because I'm old.
Kid: How old are you?
Old Man: I've forgotten.
Kid: When I forget, I look on the back of my panties. It says I'm 2 to 3.
This one is an older story from some Christian family friends:
SPOILER ALERT! IF YOU BELIEVE IN SANTA, STOP READING!
It's time you knew the truth. Santa isn't real.
Kids (with appropriate looks of shock and alarm):
No, I'm sorry.
What about the Easter Bunny??
No, the Easter Bunny isn't real either.
The kids look at each other in horror.