Matthew Patrick, or MatPat, is the owner of The Game Theorists and The Film Theorists, where he makes theories on various videos games and movies. He was featured on two of PBG's videos.
MatPat is randomly selected by PBG to have a collab with him because he is lonely in Top 8 WORST Zelda Items!. He talks when PBG doesn't want to. He is the one who collects all 3,598 rupees to get the magic armor.
PBG was listing a bunch famous Youtubers and Celebrities in Failing at Battlefield 1 (With Zac Efron). MatPat is seen and waves.
MatPat also features PBG in two of his videos.