Ninny

The Ninnies were "lithe, brutal-looking" Martians with purple skin and rugbyball-shaped heads. They had large lilac and green eyes.

A few Ninnies came to Putney Common and bought a sausage factory. The factory was secretly a front for a project to splice alien remains with kidnapped humans to create more Ninnies. Iris Wildthyme learned of this scheme, created a de-ninnificator, and defeated the Ninnies with the help of Dodie Golightly. (PROSE: The Ninnies on Putney Common)

In 1967, Brenda Soobie got one of her future incarnations to deal with a group of Ninnies so that she could host a party. (PROSE: Party Fears Two)

Behind the scenes
The Ninnies originate from Paul Magrs' storybook The Ninnies, which was published by Obverse Books in 2012. Although now named 'Martian Ghosts', the Ninnies reappeared in the Lora series books Lost on Mars, The Martian Girl, The Heart of Mars, and short story The Everlasting Match Girl with the same description of having purple skin, rugbyball-shaped heads and large multi-coloured eyes. Notably both creatures make the same "hee hee hee" sound which was originally thought to be the Ninnies' laughing but was later revealed to be their struggle to breath in Mars' new atmosphere.