Grassmarket retailer 97 Black rolled out its range of 'I heart Boaby' merchandise in tribute to the iconic Edinburgh statue just before the start of the Festival season.
However, the designs - penned by 97 Black co-owner Joanna Clark - quickly became a viral hit after locals began pointing out the suggestive second meaning.
The product description for a t-shirt bearing the logo reads: "Want to know the easiest way to make friends in Edinburgh? Declare your love of Boaby."
And co-owner Jon Clark told the Evening News he was surprised to see how popular the design has become.
He said: "We come up with a lot of animal based designs and this one just seemed funny with the pun."
"Obviously Boaby is Edinburgh's finest and we were hoping it would take off, but I don't think either of us expected it to be as popular as it has been."
Jon, 32, joked: "You never want to say everyone is 'jumping on Boaby,' but that's what it feels like."
Despite the Scottish colloquialism behind the joke, Jon insists it has been equally as popular with visitors to the Capital, adding some only became aware of the legend because of the shirt.
Jon said: "A lot of locals understand the joke and most of the people who haven't have taken it really well, they understand it is meant to be quite light-hearted."
"Bizarrely, a lot of them don't actually know the story of Greyfriars Bobby in the first place, I can imagine it is quite a weird way to find out how it originated."
Tote bags, mugs and coasters bearing the design are also available.
The full range of designs from 97 Black can be found here.