Since then, two cast members have now been confirmed for this episode, forming what seems like another duo in the series.
The episode itself is currently unknown in the running order for the series.
According to Vic Murray Talent, Dan Johnston will feature as a character named Thin Man; the actor has previously appeared as regular Jonty in Sold, a journalist in Hotel Babylon, and featured in two pilots for Thames Television, Team UK and Navelgazing: 4Tissimo.
Debi Allen Associates lists stand-up comedian Charlie Baker as Fat Man. Baker's television credits include being a panellist on Channel 4's Beer and Pizza Club and BBC2's Never Mind the Buzzcocks, and appearing in The IT Crowd; he also featured as a band singer in the film The Boy in the Striped Pajamas.
Two artists have been credited for another unknown story; Spotlight lists child actresses Fern Duncan and Frances Encell as providing voice overs for Doctor Who (filmed in 2010).
Fern has had roles on television in Poirot and in the film Gulliver's Travels, and has appeared on stage in The King and I and Annie Get Your Gun. Meanwhile, Frances has appeared on television in Emmerdale and The Royal, and on stage in Chitty Chitty Bang Bang and The Sound of Music.