The Doctor's wife, River Song, and the man who cannot die, Captain Jack Harkness, might be making a return to "Doctor Who."

In an interview with Zap2it, current "Doctor Who" showrunner Steven Moffat said he is open to having the uber popular Time Lord companions back on the show. Alex Kingston, who played River Song, has not officially confirmed anything, but John Barrowman, who played Captain Jack Harkness, is eager.

River Song and Captain Jack have been away from "Doctor Who" and "Torchwood" for a while. According to Den of Geek, the last time Kingston's Song was with the Time Lord was in 2013. The character first appeared in 2008 alongside David Tennant, who was the Tenth Doctor. Then, from 2008 to 2013, River Song made regular appearances.

Barrowman's Captain Jack not only appeared in "Doctor Who" from 2005 to 2010, but the character spawned a spin-off series titled "Torchwood." The show had four seasons that ran from 2006 to 2009, with a return in 2011, Den of Geek reported.

With the impact of Kingston's and Barrowman's characters, Moffat appears willing to have them back, but it has to work. Speaking in an exclusive interview with Zap2it, Moffat says, "It's never, ever closed off. It's all about 'Do you have a story that's worth it?'"

Moffat adds that the story has to be "absolutely informed and invigorated by their presence." In other words, bringing back the characters for an "ordinary episode" is not enough.

Having Song and Captain Jack back just to boost ratings will not work. The characters themselves are "massive characters in 'Doctor Who' mythology," Moffat notes. The return of Song and Captain Jack would not just have to whet the appetites of "Doctor Who" fans, but "their returns would have to be seismic, and not routine," Moffat points out, Zap2it reported.

Having the characters make recurring characters would not have worked either. 

"Sometimes you have to know when a story's over, you do," Moffat added. "One of the things you always want to say is 'leave them wanting more.'"

Kingston and Barrowman have a lot in common other than their iconic characters.

Barrowman is now a series regular on "Arrow," and Kingston has had a guest starring role on that show as well, but that is not how the pair met. Barrowman told The TV Addict that he first met Kingston at Cameron Mackintosh's house in London. Mackintosh is a successful Broadway producer and writer for "Les Miserables," "The Phantom of the Opera", "Miss Saigon" and "Cats."

Mackintosh was celebrating his 25th anniversary with his partner. When Barrowman met Kingston at the party, they both looked at each other and said, "Aaaaaaahh! My God!," according to Barrowman.

The pair chatted and eventually realized they were both born on March 11, TV Addict reports.

"It struck a chord with us because that's why River and Jack are very similar characters, in their attitude and their fun and their aggression, we are the same in real life -- which is really ironic," Barrowman said. "So we struck it off. Then she came on 'Arrow,' again we saw each other in the makeup trailer and just screamed. We both said, 'Boy, there's going to be some fan-gasms out there in a couple of weeks!'  It was brilliant."

Barrowman and Kingston have not slowed down since their "Doctor Who" roles. Kingston and Barrowman have both been on "Arrow," and Barrowman has guest starred on "Desperate Housewives," "Scandal" and "Zero Dark Thirty." Kingston has appeared in "NCIS" and "Private Practice."