Jean-Luc Picard

In a parallel universe,  was a Starfleet officer and the captain of the USS Enterprise-D during the 24th century.

In 2368, he sent Commander Riker on a mission to check up on mining operations on Naia VII. After an accident there, he beamed down to the planet himself. He told Geordi La Forge that Starfleet was cutting corners in safety to rebuild the fleet after their losses to the Borg at Wolf 359.

After Riker, Data and Dr. Crusher met the Eleventh Doctor, Amy Pond and Rory Williams in the holodeck of the Enterprise, Picard met them in the ship's observation lounge. He was politely sceptical of the three visitors. Their discussion was interrupted by news of the attack on Delta IV. He recognised the Borg's ships around the planet and agreed with the Doctor's sentiment that they "shouldn't be here". (COMIC: Assimilation²)

Other references
Whilst under the influence of the Syntax, the Eighth Doctor's companion Izzy Sinclair hallucinated about Captain Picard. (PROSE: Syntax)

Behind the scenes

 * The brief appearance of Captain Picard in Syntax treats him as a fictional character (as do, implicitly, other references to Star Trek and Star Trek: The Next Generation in Doctor Who stories). Assimilation², of course, treats him as a "real" individual, however the storyline clearly establishes that Picard exists in a parallel universe to the "Whoniverse", placing him in the same category as Dr. Who, the character from the Peter Cushing films who is occasionally depicted in the franchise as existing as a real person but in an alternate reality.
 * Actor Patrick Stewart was one of numerous actors considered for the role of the Eighth Doctor in the 1996 TV movie, though he has stated in interviews that he was never formally approached. During her time on Doctor Who, Lalla Ward co-starred with Stewart in a BBC TV production of Hamlet (a play Stewart later appeared in opposite David Tennant); in interviews, Ward recalls being chided by Stewart for starring in a science fiction TV series.
 * In Issue 4 of Assimilation², the Borg ask to speak with Picard and refer to him as Locutus - the name he was given when he was captured and temporarily assimilated in the two-part Next Generation episode "The Best Of Both Worlds".