- You may also be looking for the cartoon episode called by this name.
April Smurf's Day is a day of observation for the Smurfs that takes place in the cartoon show episode "April Smurf's Day", presumably around April 1. It is analogous to the human observance day of April Fool's Day, where the Smurfs are allowed to play pranks on one another so that they may be able to laugh at themselves and not take life too seriously. It is a day that Brainy and Grouchy both hate, the former particularly because Smurfs tend to play a lot of pranks on him.
On that day in the episode, Gargamel disguised himself as a living smurfberry bush so that he could capture Smurfs unaware. Papa Smurf, after finding out what Gargamel has done, summoned a flock of smurfberry birds to go after Gargamel while he rescued the Smurfs that were captured.