Vardy has been a key component in Leicester's remarkable Premier League success this season, scoring 22 goals in 34 league games, and former Foxes midfielder Guppy revealed that Martin O'Neill had instructed him to investigate the striker's heritage when he joined Ireland's coaching staff in 2014.
Unfortunately for O'Neill and Ireland though, Guppy's enquiries yielded negative results.
"One of the first things Martin O'Neill got me to do when I got the job was to find out if Vardy was Irish or not and sadly his grandparents were not," Guppy said, speaking on Newstalk's 'Off The Ball' show.
The Leicester forward eventually went on to play for England and he made his debut for the Three Lions in June 2015 against O'Neill's Ireland.
The 29-year-old Football Writers Association Footballer of the Year has made six appearances in total for Roy Hodgson's side, scoring two goals - against Germany and the Netherlands in March 2016 - and will be hopeful of going to Euro 2016 in June.