Twitter was sent into a spin after one of the 16-year-old Derry Girls recently celebrated her 31st birthday.
Written by Belfast native Lisa McGee, the Channel 4 comedy has earned widespread acclaim since hitting the small screen.
Set in 1990s Derry it tells the story of four school friends attending at all-girl school who are lumbered with an English boy who is placed in their school in order to avoid the - possible - recriminations had he gone instead to the all-boys school.
There was incredulity - and praise for her acting skills - for Nicola Coughlan on social media when one user realised just how old she really was.
Originally From Galway, Nicola plays the baby-faced Claire. She celebrated her birthday last week - her 31st making her the oldest of the five teenage characters.
"It's the rain," one Twitter user suggested while others questioned if the show was actually filmed in the 1990s - when it's set - given their disbelief of her age.
(Click on the gallery above to see how old her castmates really are...)
Nicola Coughlan, who plays Clare in Derry Girls, is 31 years old.— Amanda (@Pandamoanimum) January 11, 2018
THIRTY ONE YEARS OLD! pic.twitter.com/UKbibL8Phq
It's the school uniform that makes her look a lot younger.— zenon (@zenon2009) January 12, 2018
Must be a pain trying to get a bottle of wine from a supermarket— Gary 🇪🇺 (@garyduffynl) January 12, 2018
Actor Jamie-Lee O'Donnell has tasted stardom before as the confident, catty Eva Maguire in BBC Northern Ireland's angsty teen student drama 6 Degrees, but nothing on the level of Derry Girls.