I agree with you Philipsearching that this is looking more and more like a 19th century prank.
Indeed it was Cardinald Joseph Fesch who baptized Napoleon 2nd, he was Archbishop of Lyon and the head of the catholic church in France. I read an account of the baptism which lists who was there, only important people were named and apart from the cardinal only "the clergy of the cathedral" and "his clergy" were mentioned.
I've had answer back from the county archives, they read CS O'Callaghan, and said:
"Pádraig de Brún's Some Lists of Kerry Priests, 1750-1835, Journal of the Kerry Archaeological & Historical Society, Volume 18, has a Charles O'Callaghan as a Curate at Kenmare in 1835. He matriculated from Maynooth in August 1823, and died as PP of Ballymacelligott Parish in 1868 at the age of 76."
They also said that Napoleon 2nd never came to Ireland, so we can take that as a fact now (we have 2 reliable sources).
No answer as yet from Napoleon Ireland, I wrote to them last night.
One thing, I read that the baptism wasn't sure to go thru as Napoleon 1st was excommunicated and he was very worried they wouldn't accept to baptise his son. But they did.
I'm thinking it's either a prank OR philipsearching is right and maybe an archbishop or somebody may have assisted to represent the Irish, and he would have had an entourage of his own, our O'Callaghan was in it.
Doesn't anybody think it's odd that the person who transcribed the register on Irish Genealogy didn't say anything to anyone? And surely I'm not the first person to have noticed this! I think that the Kenmare paper should do a little research for us, they could do a fun article about it!