CBR's reporting that Black Tom Cassidy has been cast for Deadpool 2. The weird plant controlling Irish mutant will be played by Strain actor Jack Kesy.
Now his first appearance is in dispute. CGC lists it as X-men 101 but it could be X-men 99 or it could be a cameo. I really don't know what justifies a cameo these days so we'll have to let the market decide. However 101 is out of reach for most people as it's also the first appearance of Dark Phoenix so 99 may be the one to get, only time will tell !