Seems that not only will the Eleventh Doctor (played by Matt Smith) travel with known companion Amy Pond (played by Karen Gillan) but he will also have another companion in the form of Amy's own fiancee, a chap named Rory Williams (played by Arthur Darvill).
The Daily Star reports that:
He (The Doctor) is completely unaware she’s actually a stripogram girl. But the newly-regenerated Doc whisks her away in his police box and the pair are even seen sharing a snog.
It’s only later he discovers Amy was about to marry fiancé Rory Williams, played by Arthur Darvill, 27. Horrified he has split them up, he whizzes back to Earth, gatecrashes the lad’s stag do and bundles him into the Tardis
What is more, they hint that a third companion will join the group later in the series. My money is on River Song.
This will be a very crowded Tardis but it's not unusual for the Doctor to be accompanied by many companions at once. There was a time when the 5th Doctor was accompanied by Nyssa, Tegan and Aldric.