Their TARDISes have crashed into each other in the time vortex and have crash-landed on Earth as a result, combining their timelines once more. They've landed in Australia during the height of the Great Emu War of 1932. The TARDIS console room looks like a hybrid mess of each of their own unique ships as they both stepped out, giving each other the look of blame.

Tenth Doctor: "What...?! What just happened?" coughs

Eleventh Doctor: He turns around at the warped image of the two TARDISes, pulling out his sonic screwdriver and scanning the hybrid. The TARDIS makes a pained whooshing sound in response, showing both Doctors that the TARDIS is suffering from the clash. "Oh, I am so sorry my sexy girl. I'll have this fixed in a tick."

Tenth Doctor: "They both combined? I've never seen this happen before..." He says as he puts on his glasses. "Did you just call your TARDIS 'sexy'?"

Before both Doctors could investigate further, you transport in, trying to escape from a flock of emu-looking aliens. Both Doctors suddenly shift their attention directly onto you, with Eleventh Doctor now donning his own glasses.