Any Doctor Who fan will tell you they're accustomed to encountering curious creatures in foreign climes on the sci-fi series, but we doubt anyone was expecting the Doctor to meet an elephant on the river Thames.
Twelve and his companion Bill came face to face with the large land mammal in series 10 episode 3, when they set a course for 21st century Bristol (where Bill studies at university) but end up in 19th century London instead.
How do we know it's 19th century London, you ask? Well, the frozen river and the elephant give the date away.
How did an elephant end up on the river Thames?
There's a very simple answer to your question: he was put there. The Thames was known to freeze over in the 1800s, with ice thick enough to support a full-scale fair. And in 1814 in particular, an elephant walked on the frozen river as part of the spectacle.
From what we've seen of the episode so far, we're guessing something spooked that elephant, sending him directly into the path of the Doctor and Bill.
But we'll have to wait until Saturday 29th April to find out exactly what's been happening.