I recently got a dollar bill with a star next to the serial number. What on earth does this mean. I know I vaguely recall this informercial where they were bragging you could get bills with stars next to the serial number. But I forgot the reason why or soon turned off the informercial.
Thank you in advance to all who reply 
When a bill becomes too worn for continued circulation, it is sometimes replaced with a new bill. The star indicates that the bill is such a replacement.
Actually, I just found this:
http://www.straightdope.com/mailbag/mserial.html
I may have been wrong about the starred bills being used to replace worn notes; according to this, they are used to replace bills with printing errors instead. (They may also replace worn notes; I definitely seem to remember reading that, but my memory might be wrong).
The “how stuff works” article claims they are used to replace printing errors, and the error rate is about one in every 100,000 bills:
Or the mailbag, take your pick.
They were NEVER used to replace worn out bills. Period.
Interestingly(to me), they seem to have varied greatly in quantity over the years.
A specialized book I have showing numbers of notes printed would indicate that they ranged from one per hundred notes to one per multiple thousands/ Depending on the series, denomination, years, etc.
Note that the given frequencies of “per hundred notes to one per multiple thousands” doesn’t mean they actually occur as 1 mis-printed note out of a bunch of 100.
They are printing errors, which generally affect all the notes printed from a plate, until a worker notices it. This would likely be several hundred notes. Then they reprint those numbers, with the star next to them. This just happens rarely enough that the average is what was given.
If a single note out of a bunch is bad, that single note is destroyed. I believe that they don’t bother to print a starred replacement for a single bad note like that. It’s only when whole batches of numbered notes are bad that they reprint them.