Polarizing as the Moffat era seems to be, one point seems to be as close to universal agreement as you'll get online: the DW Christmas specials are on the weaker end of the programme's output. Usually little more than glorified fluff that only tangentially tie into anything, they leave much to be desired and seem to only get a pass because 'Christmas, goodwill and all that jazz'.

'The Return of Doctor Mysterio' gives us Who's take on superheroes, as a little boy is given super powers by the Doctor (accidentally, following a misunderstanding about a gem).

24 years later, New York is watched over by a crimefighter called The Ghost aka Grant Gordon, nanny for reporter Lucy Fletcher, who is investigating the Harmony Shoal corporation, as is the Doctor. The two cross paths, and before long, an alien invasion must be stopped.

'Mysterio' is the best since 'Christmas Carol'

It's the most energetic a Moffat special has felt in some time, lined with rapid fire gags and one liners while mixed in with a lot of the horror that is one of his calling cards (unscrewed heads, brains in jars, evil surgeons) that land more then they don't. There's something amusing about seeing the Doctor react off of superhero tropes, and the tone is just about right to pull it off.

It helps that the performances are all round solid, with Capaldi in fine form as always, playing a hybrid of Santa, Uncle Ben and a wearied hero over the course of the story, though Matt Lucas still feels a little underdeveloped and underused as Nardole, the new 'aide' to the Doctor. Justin Chadwick capably handles Superman Pastiche as Grant/The Ghost, going from awkward nanny to confident masked avenger with good plomp, and Charity Wakefield fills the bills of Lois Lane well, though her material is more limited.

Aleksandar Jovanovic and Adetomiwa Edun have fun as the ruthless villains, though they are given little to do beyond rant or threaten.

The production values are good as ever, creating a feel akin to the Richard Donner and Fleischer Superman films with a slightly stylized New York right out of a comic, and several scenes paying homage to that iconography (including a flight across the city, a rooftop interview between Fletcher and the Ghost, and even the famous bullets bounce off bit).

Murray Gold's music is not among his best, but he does throw in some fun nods to John Williams' iconic theme in his take on an epic superhero score.

Still, 'Mysterio' feels a bit insubstantial

The relationship between Grant and his love doesn't feel as well rounded as it could, even with the domestic element taking a greater focus, and the villain scheme feels rehashed from the Slitheen two parter in Series 1, and doesn't feel as well woven in as it could. It felt like Moffat had a really solid satire of superheroes, toying with the idea of Grant's shyness and wish fulfillment, but then lost focus and wrote another alien invasion plot that doesn't really tie that much into Grant's own arc about maturity from a thematic viewpoint.

In closing, 'The Return of Doctor Mysterio' makes for a decent romp, with enough humour and references to make it pleasant, but it does little to cast off the popular image of Christmas specials as fluff, and it won't win back cynics of Capaldi's era.