An anonymous artist from Carmarthenshire has installed 170 hoax notices on roads across Wales and the UK over the last two years.
The project aims to raise awareness of signposts left empty because they are too costly to remove.
The artist said the empty posts were a "very tangible symbol of neglect".
The fake signs have featured slogans saying "be kind", a warning worms may be "slippery and wriggly" as well as a birdbox in Swansea, which was disguised as a speed camera.
Despite the light-hearted messages of the signs, the artist said there is a serious issue behind the project, which he calls "Lonely Signpost".
He said: "The art works' intention is not to cause problems but merely to highlight the issue of 'empty signposts'.
"We almost do not see them until we start looking, then we see how widespread and obvious they are.
"Standing everywhere doing nothing, littering our beautiful countryside, a very tangible symbol of neglect."
Joke messages are appearing on empty roadposts on country lanes as part of an art project to highlight the number of empty signposts in Wales.