The Herald understands that the clown blew up balloons and folded them into a series of animals throughout the meeting.
It's further understood that the clown mimed crying when the redundancy paperwork was handed over to the staffer.
Thompson - who has created social media accounts under the name Josh Jack, a budding comedian - told the Herald this afternoon he had since returned to Australia.
He has secured a new job with DDB and is expected to start in the role next week.
And in an interview on MediaWorks, Thompson admitted that the choice of his support person had been a "touch unusual".
He called on the services of a clown - who he has dubbed Joe - after getting an email earlier in the week telling him "bad news, we're having a meeting to discuss your role".
"I thought it's either a promotion or worse. I thought it's best to bring in a professional and so I paid $200 and hired a clown," he told MediaWorks.
"I mean I did get fired, but apart from that it was all smooth running."
Thompson said the clown made several animals out of balloons, including a unicorn and a poodle.
"It was rather noisy him making balloon animals so we had to tell him to be quiet from time to time," he said.
He also revealed he had spent $200 on the services of the clown.
"Basically he was, I assume, one of the best clowns in Auckland - they were getting a free service, they were also getting the entertainment from Joe the Clown."
A spokesperson for FCB told the Herald the agency has a policy of not commenting on individual employment matters out of respect for those involved.
In an email title "Coulrophobia" (the fear of clowns), the spokesperson did, however, say it was up there among the weirdest stories she had ever been contacted about.
The latest restructure at FCB follows on from job cuts at the agency after the loss of the Vodafone ad account.
