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".

Captain Picard then commanded for a red alert and for the Enterprise to raise shields. Their vessel had fallen under attack by the Borg/Cybermen alliance. Data was soon commanded by Picard to find cover in a nebula which he did. The Doctor soon relayed any and all knowledge of the Cybermen to Captain Picard and he at an instant distrusted him. He soon learns from Data that the Cybermen came to their universe before and the Doctor soon regained those memories. After that though, Captain Picard took the Doctor, Amy, and Rory to Guinan in Ten Forward.

Picard had to ask Guinan if the Doctor could be trusted and she assured him that he can be. An attack on Cogen V was soon learnt of and an away team was sent to the planet. After examining Borg and Cybermen casualties, it was learnt that they turned on each other. The Borg reached out to Picard to forge an alliance, but he grimly refused.

After sharing his history with the Borg to the Doctor, the Doctor tried to convince Picard to form the alliance. It was all for nothing so then Counselor Troi suggested that Amy speak with him. Which she did and Picard was asked to go to the holodeck to see "something". Picard was taken into the TARDIS and then he was taken into this universe's future. Because the alliance was not met, the Cybermen converted the Borg and soon converted and enslaved both universes. After seeing these horrors, Captain Picard finally agreed to the alliance with the Borg.

Then on planet Tau Lee along with an away team consisting of: himself, the Doctor, members of the Enterprise, and the Doctor's companions, the alliance was made. A Borg drone called the Conduit intended to aid the Enterprise in any way to eradicate the Cybermen because assimilation was impossible. The Doctor told Picard that the Cybermen have an aversion to gold so they beam to the planet Naia VII to ask the inhabitants for the gold. It was the Doctor that managed to get the resident Seelos to give the Enterprise the gold. As the Doctor intended to go back in time to the battle of Wolf 359, Picard and Riker wished to go with him, but the Doctor refused.

The Doctor and his companions met Picard's assimilated form Locutus and after a few near misses, they returned to the future with the Borg Executive Library. Picard led an away team to the main Cyber-Ship and after another near miss: the Doctor, Picard, Data, and the Conduit made it to the Cyber-Controller. He was defeated and the Borg were restored to full power. Captain Picard then bid farewell to the Doctor and his companions. Although he was happy that the Doctor came when he did, Picard admitted that he hopes that he and the Doctor never have to cross paths again. (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 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".