In Alabama is an employee required to pay back an employer for an over payment in wages that was on a check stub as a bonus ?

Was it an overpayment by mistake or was it a bonus?  If it was an overpayment, yes; if it was a bonus, no.  If the two sides have different stories as to which it was, a judge or jury will decide, although the check stub does seem like pretty good evidence that it was a bonus.