The episode reintroduced actor and comedian Catherine Tate as Donna Noble, who had previously appeared in the 2006 Christmas Special "The Runaway Bride".

In the episode, Donna and the alien time traveller the Tenth Doctor (David Tennant) meet while separately investigating Adipose Industries, a company that has created a revolutionary diet pill.

The episode's alien creatures, the Adipose, were created using the software MASSIVE, commonly used for crowd sequences in fantasy and science fiction films.

Most reviewers praised the visual effects used to create the Adipose and Tate's subdued acting in comparison to "The Runaway Bride"; Donna was changed from a "shouting fishwife"[2] to a more emotional person when she became a full-time companion.

Critics were polarised over the episode's plot: opinion on executive producer Russell T Davies' writing ranged from "pure pleasure"[3] to "the back of a fag packet".

The Doctor and Donna, neither one aware of the other's involvement, both investigate Adipose Industries, which is marketing a special diet pill to the people of London.

The Doctor tries to warn Miss Foster about her safety, but she disregards him and is killed when the Adipose drops her from their transport beam to her death, to cover their unsanctioned seeding efforts.

Donna makes a detour to leave her car keys in a litter bin, telling her mother Sylvia to collect them later.

[5] Tate's return was controversial amongst Doctor Who fans; the criticism she received was compared to Daniel Craig after he was cast as James Bond.

[5] Producer Phil Collinson suggested transferring his traits to the unrelated character Stan Mott from "Voyage of the Damned", and rewriting his role as Donna's grandfather.

The scene was filmed in Picture Finance's call centre on the outskirts of Newport on an early Sunday morning, with the company's telephonists serving as extras.

[5] Exterior shots of Adipose Industries were filmed at the British Gas building (Helmont House) in Cardiff's city centre.

[12] Stephen Regelous, who won an Academy Award for his software Massive, flew to London to supervise the creation of the crowd special effects.

He liked the Adipose's execution of Miss Foster, a "momentary pause in mid-air, gravity only kicking in when the character looks down", comparing it to Wile E. Coyote and Chuck Jones, which "[was] a nice little touch in an episode ... full of them".

[23] Sam Wollaston of The Guardian wrote that Tate was "not right for this role" and "too hysterical, too comedy, not cool enough", and felt her inclusion was an attempt to trade on the popularity of her own series and "broaden the appeal of [Dr Who] still further".

[26] Ben Rawson-Jones gave the episode a wholly positive review, summarising it as containing "pure fantastic family fun, delivering a winning blend of action, comedy, poignancy and one unexpected shock cameo".

Andrew Billen, writing for The Times, lamented that Davies had "forgotten that Doctor Who's main task is to send children scuttling behind sofas while entertaining their fathers with the odd philosophical idea, the occasional classical reference, a joke or two they would probably not wish to explain and a wee bit of space totty".

[28] Alan Stanley Blair of SyFy Portal summarised it as "a runaway Saturday morning cartoon in desperate need to a solid story".

[29] Kevin O'Sullivan of the Sunday Mirror criticised Tate and Tennant for overacting, and had concerns about the writing: "It didn't exactly ooze tension.

All we got in the way of terrifying space enemies was Sarah Lancashire hamming it up as an intergalactic super nanny, a couple of security guards with guns and lots of cute little fat babies.

[4] Reviewing in 2022, Mark Braxton for Radio Times described the return of Tate as a "casting coup", and opined that Donna and the Doctor paired better than previous matchups in the series.