Why can't anything get colder than absolute zero

Nope.

Absolute zero (0 kelvin) means minimum entropy, so it just can't get any "colder". It is worth noting that it is not achievable, through thermodynamic means, though it is possible to get very close (scientists have achieved a femto-kelvin, or 0.000 000 000 000 001 K).

Also, absolute zero doesn't mean lack of energy, nor lack of movement. It means lack of thermal energy. Even particles at absolute zero have a minimum of vibration (ground state kinetic energy, also called zero-point energy) that can't be removed by any means.

cos if it could then the new lower temperature would be absolute zero

its called absolute zero cos whatever is at that temperature has zero energy (heat = energy)
To get to a lower temperature it would have to lose energy, but it aint got any more to lose, so it just cant get any lower. (its IMPOSSIBLE)

In our Universe absolute zero can never be reached let alone colder than that temperature as we understand Physics today. Absolute zero can never be reached because of Quantum Theory concerning fleeting virtual particles. Thanks for an earlier post to this question, I now know what negative energy and what I need to hold open a spaceship sized wormhole.

It is because cold is the absence of heat. Once ALL the heat is removed, the temperature would be absolute zero and there would be no more heat remaining.

You can't take away more heat than all of it.
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because "cold" is just the lack of movement from the particles, so when you hit -273c there is absolutly no movement at all from the particles hence the term "absolute zero"

heat is when particles vibrate. When there is no movement they are at absolute zero and they can't get colder because they already are still.

Heat is a measure of 'energy density'.
There is no such thing as negative energy.
(The photon is it's own anti-particle.)

It can and it does, but if something does it's on other planets, ex. Pluto

Yes it can