According to the episode "Happy Birthday, Barney!" Barney is two hundred million years old or two dinosaur years old.

How old is Barney now?

The character of Barney was created by Sheryl Leach in 1987, which would mean Barney is currently 32-years-old.

Why did Barney go to jail?

The silliest of these rumors, which still pops up from time to time, is that the "actor who played Barney" (who is nameless, in this story) was actually a crazy cocaine addict, supposedly so addicted that he hid his prized cocaine stash up Barney's purple tail, which eventually got him caught and thrown in jail.