In 2009, Greg had made 4 videos about Shane Dawson, including some in response to some video commenters saying he looks like Shane. One of the remaining videos was "SHANE DAWSON!? NO!", uploaded on November 18, 2009. Although most of the video has nothing to do with Shane, in the middle Greg says, "Hey look everybody. I have long hair and I'm white. I must be Shane Dawson because we're all racist a-holes." ($ource)
In December 2009, Shane saw the videos and contacted Greg to do a video collaboration with him. On December 10th, Greg uploaded "Dawson's Freak", where he overreacts to Shane's message. ($ource)
On December 12, 2009, Greg and Shane uploaded their collab videos to their channels. Shane recently had a surgery, so he could not make a video that week. He had Greg pretend to be a Shane Dawson impersonator for his video. (Source) Greg uploaded "SHANE DAWSON FANBOY LOVE!", where he pretended to be an obsessed fanboy that paid Shane to make an appearance in his video. ($ource) This collab, along with a collab with SwiftKarateChop, helped Greg's subscriber rank skyrocket and put him on the map in the YouTube community of the time.
In 2010, Greg made a theme song for Shane's videos, which he had done for several YouTubers during this time. (Source)
End of Friendship
Shane mostly ignores most of Greg's attacks and tweets. He will very rarely joke in videos about how much Onision hates him. His fanbase is very much aware of the beef between Shane and Greg and will joke about Onision in the comment section of Shane's videos.