The Reginald Barclay hologram was a hologram created by the Lieutenant Reginald Barclay as part of the Pathfinder Project in 2377. It was meant to be transmitted to USS Voyager in the Delta Quadrant through the datastream via the MIDAS array.
When regular datastreams were possible with the Voyager, Barclay proposed sending a hologram instead of normal transmissions of reports and messages since a holographic matrix could store twice as much information. His supervisor, Commander Peter Harkins, agreed and the hologram was created. Barclay designed the hologram with a personality profile based on himself, but with a much more confident demeanor.
When it came time to transmit the hologram, however, two attempts to send it failed because they were intercepted by the Ferengi Nunk. On the first attempt, Nunk had the hologram altered in order to carry out a plan to trick Voyager to come to him in the Alpha Quadrant by entering a geodesic fold. This would kill all of Voyager's crew, but the hologram was to be convincing enough to fool them. Nunk was after Seven of Nine's nanoprobes, which would be worth billions of times their own weight in latinum. The hologram was further altered to ensure Seven specifically entered the fold. He then sent the altered hologram on to Voyager during the MIDAS array's second attempt, where they remained unaware of the modifications.
The Barclay hologram nearly succeeded, having interacted well with the crew on both professional and personal levels, until the real Barclay at Starfleet Headquarters discovered the plan. The real Barclay impersonated his hologram in a communication and tricked Nunk into closing the geodesic fold before Voyager could enter it. This gave cause for Kathryn Janeway to cancel the procedure, however, the Barclay hologram instead left Voyager with Seven, who he had incapacitated, in an escape pod and attempted to enter the closing fold. Harry Kim beamed them out before they could reach it and the program was deactivated there.