The trio have been added to the squad to face Tonga on Friday Night in Thomond Park.
Along with the three well known faces added are Irish and Leinster flanker Jordi Murphy, former England and British and Irish Lion Geoff Parling, as well as wingers Taqele Naiyaravoro and David Smith.
This will be O’Callaghan’s second stint with the Barbarians after featuring in their win over England back in 2014.
The two Munster representatives have been included in the invitational side for the first time in their career’s, in what will be the first time the side have played in Limerick since their 22-21 defeat of Ireland in 2015
Cronin said: “I was watching the (New Zealand) game on TV at the weekend and chatting with my buddies about it, and it’s a special thing. You get to wear your club socks and represent where you’re from, and it’s such a prestigious club. It’s an opportunity everyone wants.”
Scott is delighted with his inclusion and says it’s a huge “privilege” to be chosen to represent such an historical side with so much talented players having already worn the famous black and white.
He said: “I know what a great honour it is to play for the Barbarians and I’ve seen some unbelievable players over the years and I know what a privilege it is to wear the shirt. There are players coming in from all round the world, all great players, and it’s fantastic to be involved and to do it at Thomond Park.”
The two wingers added to the squad will add huge attacking threat, with the 6ft 5in Naiyaravoro well known in World Rugby for his physical prowess and speed for such a large build.
Smith on the other hand, who plays for Munster’s Champion Cup pool 4 opponents Castres, is of a much small and stockier build and is known for his superb speed and finishing ability, traits which first brought him to France when he was signed by Toulon a few years back.
Geoff Parling started all three 2013 Lions tests, has made 194 top flight appearances for Leicester, Exeter, Newcastle before joining Munakata Sanix Blues in Japan.
Murphy has made 17 appearances for his country, with his last coming in Ireland’s first ever win over New Zealand in Chicago last year.