The One With The Hypnosis Tape - S3-E18
Corrected entry: When Monica shows Chandler the check from Pete, Chandler says, "Pete Becker, Pete," and he grabs a magazine from his briefcase, but before this Chandler told the girls that he hasn't been able to unlock the briefcase and he just carries it around, so how would Chandler have gotten it out?
Correction: Chandler pulls the magazine from a pocket on the side of the briefcase.