Michael frequently "fake fired" people on "The Office," seeming to enjoy the power he held over the fates of others. 

The first instance came in Season 1, when he pretended to fire Pam in front of Ryan (B.J. Novak). For some reason, this was hilarious to Michael, who never seems to understand how much he's hurting the person he is pranking. In that instance, after telling Pam he was just kidding, she called him a jerk and began to cry, leaving him acting offended. 

He clearly didn't learn from this, as in a later episode when Dunder Mifflin absorbed the Michael Scott Paper Company, and he once again told Pam she had lost her job — this time, a highly-valued sales position she had supposedly ceded to Ryan.

But the fake firings didn't stop at Pam. Perhaps thinking he was on a roll after messing with Pam for a second time in Season 5, Michael had her call Erin (Ellie Kemper) into his office so he could play the same prank on her. Not only did he tell her that he had to let her go, but Michael also mentioned to Erin that by the way, no one in the office liked her. In Michael's mind, a laugh and assurance it was all a joke made everything all right — but even though the sweet Erin laughed it off alongside him, he had nonetheless planted a hurtful seed that seemed to imply Erin's colleagues hated her.