The 50-year-old actor joined the cast of the sitcom as Mike Hanningan, Phoebe Buffay (Lisa Kudrow)'s eventual husband, for its ninth season, but he didn't get off to a great start when he accidentally hurt one of the lead cast members.
He recalled: "I was on the set for my first episode and Jennifer was on a Segway because she had broken her toe, and everyone was marvelling at it.
"Matt LeBlanc asked to have a go and immediately knew how to do it.
"I then asked to try it too. I spun round and rolled it right over Jennifer's foot!
"The producers look of panic was if to say, 'Is it too late to fire him? Has his character been established yet?' I felt awful. Such an inauspicious start."
Paul admitted it was "incredible" and very "surreal" to be involved in the popular show - which is celebrating its 25th anniversary - and recalled another awkward moment, on the very last day of filming.
He told talk show host Graham Norton: "It was an incredible thing to be part of and the whole experience, but seems a bit surreal and a bit of a blur in my memory.
"The show was a phenomenon and I was in the very last episode, which made no sense to me whatsoever.
"I was on the sound stage and Jennifer Aniston was crying and I thought, 'I'm not supposed to be here, so to break the ice I went over and said, 'Well, we did it, what a ride.'
"The joke inevitably fell flat!"
The full interview with Paul airs on 'The Graham Norton Show' on BBC One on Friday night (11.10.19).