Mike joined The Roots on 75 Bars rapped most of the first verse of I Have Not Begun. This was not an impromptu performance as a soundcheck video of the collaboration exists.
Other Notes:
On January 31, 2010, Mike posted a video to his blog with the description saying, "I went onstage with The Roots last night at about 2:30am. Here’s the clip." It was later discovered in November 2010 when LPUX launched that the song Mike rapped over the jam was part of I Have Not Begun, a 2009 Linkin Park demo.
In 2018 interviews after he played Jimmy Fallon with The Roots, Mike discussed this show. He said that he was very prepared for the verse he was doing over 75 Bars, but when it came time for the show, the band was playing the tempo almost twice as fast due to being under the influence so he felt like he could barely get the words out to it intime. Mike said it was cool, but he'd like to do it again since he felt that his performance was a little underwhelming.