Farnaby was a long-time member of The Mighty Boosh supporting cast,[4][5] having had roles both in their series and co-starring in the quasi-spinoff film Bunny and the Bull.

[6] Other notable television work includes recurring roles in the sitcoms Jam & Jerusalem,[7] The Midnight Beast[4] and Detectorists.

[7] Farnaby has presented a number of factual programmes including Richard III: The King in the Car Park in 2013,[8] tracing the discovery and identification of the remains of the last Plantagenet king, the 2014 Channel 4 documentary series entitled Man Vs Weird, in which he travelled the world investigating people who claim superhuman abilities,[9] and as narrator of the Channel 5 docu-series called On the Yorkshire Buses, following East Yorkshire Motor Services.

[2] Farnaby has worked extensively with the Them There collective of six writers and actors, who started as principal members of the cast of the CBBC live-action series Horrible Histories, where he played offbeat characters including Caligula and Death.

[24] Farnaby subsequently appeared alongside Paddington Bear and Queen Elizabeth II in a short film broadcast as a part of the Platinum Party at the Palace for the Platinum Jubilee of Queen Elizabeth II in June 2022, which won the 2023 BAFTA for memorable TV moment, which Farnaby accepted.

[2] Farnaby is the co-writer of 2023 Christmas release Wonka, along with Paul King, which is a prequel to Charlie and the Chocolate Factory by Roald Dahl.