Once a Sim becomes a 4-Star Celebrity (Proper Celebrity), they will be automatically given a special “Fame Shine” that indicates they are a “big time” celeb. This happens to Sims that are in the active household, and to random celebrity townies in the world.
You can download this mod to completely remove this shine from the game, or use the “Turn off Fame Shine” self-interaction on your Sims and NPCs. You will have to click every Sim with shine to turn it off. There is not a “turn off for all” option in the game.