Theory:Doctor Who television discontinuity and plot holes/Death to the Daleks


 * What happened to the Exxilon in the TARDIS after Sarah knocks it out?
 * There is no reason to assume it would have stayed in there once it regained consciousness.
 * The TARDIS is a big place; maybe he got lost and stayed there. I imagine he and the lost Cybermen had a nightly poker game, with Kamelion joining in for a year or so, and eventually those two Saudi guards from Interference. He might have eventually become the stowaway companion with the longest record for hiding out before being found, if only he hadn't died horribly when the TARDIS transformed into the Edifice between Shadows of Avalon and The Ancestor Cell. (Even if he survived that, nobody could have survived Marnal's fusion device, the 11th Doctor's regeneration explosion, the Big Bang explosion, and the TARDIS erasing itself from history to be remembered back by Amy, unless their name happened to be Davros or Koschei.)
 * The TARDIS is a big place; maybe he got lost and stayed there. I imagine he and the lost Cybermen had a nightly poker game, with Kamelion joining in for a year or so, and eventually those two Saudi guards from Interference. He might have eventually become the stowaway companion with the longest record for hiding out before being found, if only he hadn't died horribly when the TARDIS transformed into the Edifice between Shadows of Avalon and The Ancestor Cell. (Even if he survived that, nobody could have survived Marnal's fusion device, the 11th Doctor's regeneration explosion, the Big Bang explosion, and the TARDIS erasing itself from history to be remembered back by Amy, unless their name happened to be Davros or Koschei.)


 * A Dalek is killed by the freezing lake, but it apparently has no effect on humanoid tissue.
 * The Dalek also fell off a cliff prior to hitting the lake. The freezing lake may only affect the machine elements of the Dalek, including the Dalek's life support system.


 * How did the Daleks complete the puzzles in the city, which are mostly touch based, when touching is supposedly the one thing a Dalek can't do?
 * Daleks do come with attachments just for these situations, or perhaps got one of the Exxilons to do it for them.


 * How does the Dalek voice synthesizer and flashing dome lights operate with the power drain in effect? The same psycho-kinetic power they use to move also?
 * Sure, why not?


 * Four Daleks exit the ship at the end of part one - and all agree to go with the Humans. But later, when they are attacked by the Exillons, they blow up one and take two to the prison - what happened to the fourth?
 * It returned to the Dalek's ship and reported what had happened.


 * Effervescent water - as described at the start of the first episode - would not give the illusion of additional buoyancy to a swimmer as The Doctor claims. For the bubbles to rise they would need to be less dense than water, and their presence would therefore reduce the overall density of the liquid. This would make Sarah Jane more likely to sink, not more likely to float.
 * Depending on the nature of the effervescence, the pressure of the gas bubbles rising would be enough to support a swimmer.


 * Mythbusters have been at this one, and determined that the upward current of the bubbles would indeed counteract the lack of density (though whether that would actually translate to additional buoyancy is another matter).