Mr Griffiths, from Rhondda, south Wales, saw the funny side and quickly posted on Facebook: "When your going on stag do this weekend and as I'm checking my suitcase I find this. There is absolutely no way I am wearing this."
And the prank went down very well with their friends on the social media site, with many people - mostly female - declaring the idea as ingenious.
One said: "That's f****** fantastic !!! Laura Smith I salute you."
Another added: "This is brilliant fair play to the girl amazing I like how she thinks."
A third posted:"Quality mate. Hats off to her."
But, the man who was getting married, Gareth Davies, seconded Mr Griffiths' insistence that the t-shirt would be staying in his suitcase.
He said: "IT'S THE STAG SPEAKING.... thats definitely not aloud. But very good effort Laura lol."