About

“OO YEE”, sometimes written as “ooh yee” or “ohye”, is a catchphrase that is often used in discussion threads to imply that someone is seeing a booty oo yeeeeeeeeeeeeeeeeeeeeeeeee.
The phrase “oo yeeeeeeeeeee” is a dissing technique found in the context of dank memes, with its roots in bootys. The phrase can be often heard on very memey sfm undertale videos or songs primarily intended to mix the OO YEE sound with the melody.
Origin

The first oo yee video ever was submitted by user Fanic on Nov 30, 2015, named as 'ooh ye – the movie '

Spread

On Feb 10, 2016 youtuber Fanic uploaded Every UNDERTALE Parody Ever video, featuring OO YEE from 0:33 to 0:50, this video has reached over 620K views as of 18th of May.

Shortly after, there were a lot more videos featuring oo yee and remixed in famous songs from UNDERTALE or TF2 like Megalovania and Intruder Alert.

OO YEE TF2 Mod
On April 20, 2016, youtuber Fanic uploaded a Team Fortress 2 Mod named 'OO YEE Mod' this mod replaces a lot of existing voice lines from the guy with OO YEE and also changes the hitsound and some music.