He appeared in an Oculus Rift video, a Turbo Dismount video and in the 500,000 subscribers special. In the Turbo Dismount video he does the intro, only for Jack to come out from the bathroom and force Killian out of his chair. Jack later explained that it was a joke for Killian to do his intro while he went to the toilet.
He also appeared in Jack's ALS Ice Bucket challenge, where, after Jack poured water over himself for the cause, Killian poured more water over him from a window above.
Unfortunately, Killian moved out sometime in 2015, including all of Jack's roommates, leaving Jack by himself in their apartment until Signe lived with him.