showing £4.79 for me!? This must be just via Amazon devices, as you cant get it for this price on normal google play store etc

its on the amazon app store

amazon.co.uk/Dis…CX0

DuckTales (oooh ooooh):D

You purchased this item on 28 Aug. 2015.

I've got a long list of games never to be played lol

Well it's also showing on my acer android tablet but it might be because there's a fire on my account?

Aren't most apps on Amazon Underground free? Thought that was the point of Underground .... Free apps and all unlocked .... Amazon inject their own adverts into the game between levels to 'pay' the royalty fees

No there's loads of paid for stuff on Underground too, i don't really know the point

.....​please note the use of the word 'most'......
Having a free app on Underground isn't really a deal, it's the norm.