I see this quite a lot and I have seen it's from some anime but yeah?
Also like every Pokemon player on Youtube celebrates over 9000 subs.
Over 9000 is a meme made famous from the anime Dragon Ball Z, in which Vegeta uses a scouter (a device to measure strength in a person) on Goku, to see that his power level is astronomical, or, "over 9000."
Over 9000 video
It's from dragonball z. Some guy said "My power level is over 9000!" That's all I know. Hope this helps! :)