The mysteries of time and space can be difficult enough to comprehend, without throwing in all the various rumors of upcoming castings and reunions of 'Doctor Who,' but we thought we'd take a sonic screwdriver to the cloud and point out some of the more interesting tidbits.

Not only has production begun on the seventh series of Matt Smith's tenure as 'Doctor Who'  but fan attention is particularly drawn to the 2013 50th anniversary special , for which it's very possible that a number of past 'Doctors' could pop up, regenerations aside.  Tenth Doctor David Tennant and Seventh Doctor Sylvester McCoy have expressed interest, while Ninth Doctor Christopher Eccleston assures he won't be back and even Fifth Doctor Peter Davidson expresses doubt in such a reunion.  Current Doctor Matt Smith has expressed hope to recruit as many as possible.

But there were a few numbers missing from there, no?  Well, good news!  In a recent interview with Digital Spy, Eighth Doctor Paul McGann confirmed his own interest, saying "being 'Doctor Who,' there's always anniversaries looming large—celebration programs and episodes. I'm often asked, if they get the five Doctors together, would you do it?' and of course, I'd do it.  They've just got to ring me up!"

McGann played the Eighth Doctor in the somewhat-reviled 1996 TV movie opposite Eric Roberts as "The Master," but remains in the canon nonetheless.

But what's more?  Heartbroken that fans may be over Karen Gillan and Arthur Darvill will exit 'Doctor Who' as Matt Smith's companions following the seventh series, the hunt for news of the Doctor's new companion(s) only intensifies.  Bleeding Cool has begun to make a case that one-time guest star (and Ninth Doctor David Tennant's ex) Sophia Myles might be the one to earn a key to the TARDIS, based on a few circumstantial facts.

For instance, the site points out that 'Doctor Who's seventh season recently filmed in Spain, the same location Myles recently tweeted about traveling to.  Not only that, but Doctor Who showrunner Steven Moffat and Myles have been observed to become quite chummy over the social media forum in recent weeks.

Furthermore, Myles is scheduled to appear at a Doctor Who convention later this month, and was even recently interviewed by Doctor Who Magazine, who offered no context for the placement of the interview, yet claim to know who the next companion will be.  Interesting...

What say you, 'Who'-vians?  Who would you most like to see return for the 50th anniversary special, and who are your pics for the next companion?  Take some timey-wimey time and give us your dream picks in the comments below!