Why did tea help the Doctor come back to reality in The Christmas Invasion?

Simple – Caffeine! He would’ve gotten better results with the all-holy coffee, but that’s just my opinion. Tea contains a trace amount of caffeine, as do most morning beverages. That’s why they’re called “pick-me-ups”.

Emony Stein

What happened to the companions in Time Crash?

They were a variable, and the Doctor was a constant in the time/space continuum. They couldn’t exist in the rupture caused by the collision of the two TARDISes, so they were canceled out as a factor, to be added back in later.

Jonas Roderiguez

Why does the Doctor typically pick up female companions?

Normally, Em would take this one, but let’s give it to Jonas.

Well, as the country duo Brooks and Dunn once said, “If your life’s got something missing, just put a girl in it.” The Doctor, especially after the destruction of Gallifrey, felt a loophole in his life and decided to fill it with a girl. Also, his being a guy explains a lot of it. Guys tend to want to hang around girls, especially “ladies’ men” like the Doctor.