Grouchy Smurf

Long ago —so long ago that nobody can remember — Grouchy Smurf was a more-or less normal Smurf. But he never got over the incident when a Bzz fly attacked the Smurfs. Maybe he was allergic to the sting.

In any case, every single day since then, Grouchy wakes up on the wrong side of the bed. He goes around with a scowl on his face, always part of the gang yet slightly apart, his arms hanging at his side as he mutters to himself about all the things he hates: windmills, dancing, jokes, dragons, picnics, meows, kaboom, olive pit, etceteras, etc.

That pretty much sums up everything he says — who knows what else goes on in his mind? Because every once in a while, when nobody is looking, he exhibits a secret love for something, like flowers. And he finds it impossible to hide his love for Baby Smurf, who reaches right past Grouchy’s wall of grumpiness and puts a little glow into his heart.

Backstory
In the comic book story "The Black Smurfs", Grouchy Smurf started off as one of the generic Smurfs gathering to work on the village bridge, though he disliked working at most times and wanted to take a nap until he comes face-to-face with Papa Smurf, as the latter orders him to cut a pole in the forest.

As he was merely working on chopping down his first tree, he finds himself bothered by the Bzz Fly who annoyingly circles him. This causes Grouchy to give chase towards the Bzz Fly, he doesn't notice that the Bzz Fly has secretly flown behind him, and stinging him in the tail that turns his skin jet black (purple in the Papercutz releases) and reducing his vocabulary to the single word "gnap!".

Papa Smurf would order some of the Smurfs to capture Grouchy and take him quarantined in his house until Papa Smurf finds out the cure to the contagious disease. However, Grouchy wouldn't be contained in his house for long as he would soon break out of his bonds and bites the next Smurf outside the house, turning that Smurf black as well.

Grouchy, as the first Black Smurf, overhears that the Smurf Village has found out that tuberose pollen is antidote to his disease, he paints himself blue to give the impression that he wasn't stung by the Bzz Fly. What's more, this gave him (for the favor of the other Black Smurfs) the advantage of biting the other Smurfs him getting sprayed with the antidote.

In the end of the comic book story, when everyone was cured, some of the side effects of Grouchy being a Black Smurf remained a part of him as he was likely allergic to the sting of the Bzz Fly and that he never got over the incident ever since, giving birth to his grouchy personality we all know as of today. This would be explained by other Smurfs who took note of his behavior in The Egg and The Smurfs.