William Riker
Commander Riker was the first officer of the USS Enterprise.
Captain Picard sent him on a mission to check up on mining operations on Naia IV. Taking Data and Worf with him, he discovered that the mines, which were below the water level of the largely aquatic planet, had been constructed with insufficient regard to safety. In fact, a section of the mines flooded while he and his team were visiting, and Riker was saved from drowning by Lt. Cmdr. Data.
After Riker returned to the Enterprise, Capt. Picard suggested that he inspect the ship's holodeck, which had just received a systems upgrade. Accompanied by Data and Beverly Crusher, he began a Dixon Hill programme set in 1940s San Francisco. He heard the Doctor's TARDIS materialize, but thought it was a bug in the upgrade. Similarly, when the Doctor, Amy and Rory arrived and the Doctor identified Data as an android, Riker assumed that the simulation was malfunctioning, recognizing Data as an anachronistic element in the setting. He ended the programme and was surprised to see that the Doctor, Amy, Rory and the TARDIS were not part of the simulation. After Worf escorted the trio to the ship's observation lounge, Riker asked Deanna Troi if she could sense anything from their visitors. The introductions were interrupted by news of the attack on Delta IV. (IDW: Assimilation²)
Behind the scenes
As of issue #2, Commander Riker's first name has not been revealed in Assimilation², so from the point of view of the Doctor Who universe he's just "Commander Riker" so far.
