"I'm a threat!" is a quote said by Donkey in the fanmade DEATH BATTLE "Finn and Jake VS Shrek and Donkey" created by a user known as "Death batle" on May 31st 2015. This quote is said before "Jake responds quickly gets bigger your foot and hits donkey, is launched at 20 meters high, falls but does not survive the fall".
This quote is usually copied and pasted in the chat alongside "Sherk: My leg!" and often used by Hipper and 5555thExplosionMage. It is unknown when the meme became a meme.