https://legacy.curseforge.com/wow/addons/tidy-plates-threat-plates?comment=7329

Not a bug or anything I think. But in Cata Classic, when a mob dies, its name in red and level in yellow below it appear for a split second right below where the health bar was.

Its not huge or anything, but its a bit distracting and for the life of me dont know what setting that is. Its never happened before this week.