Ciaran Gribbin (born 1976) is a Northern Irish singer-songwriter, guitarist and producer who hails from Castledawson, Northern Ireland.
Steven Patrick Morrissey (born 22 May 1959), professionally known as Morrissey, is an English singer, songwriter and author.
 He rose to prominence as the lead singer of the indie rock band the Smiths, which was active from 1982 to 1987.
 Since then, Morrissey has had a solo career, making the top ten of the UK Singles Chart on ten occasions.
"Celebration" is a song recorded by American singer and songwriter Madonna for her third greatest hits album of the same name (2009).
 It was written and produced by Madonna, Paul Oakenfold and Ian Green, with additional writing from Ciaran Gribbin.
 The song was released digitally on July 31, 2009 by Warner Bros.
 Records.
 Madonna collaborated with Oakenfold to develop a number of songs.
 Amongst all the songs developed by them, two were chosen for the greatest hits album with "Celebration" being released as the first single from it.
 It is a dance-oriented song with influences of Madonna's singles from the 1980s and 1990s, and consisting of a speak-sing format bridge.
 The lyrics of the song invites one to come and join a party.

Question: what does Morrissey and Ciaran Gribbin have in common?
Answer: singer