An early television role was in the controversial gangster drama Big Breadwinner Hog in 1969, and between 1971 and 1975 he made regular appearances in Z-Cars as Sergeant Culshaw.

Challis appeared on the Channel 4 mockumentary television programme Brass Eye, where he was tricked into believing Clive Anderson had been shot by Noel Edmonds. On BBC radio, he played an interrogator in the play Rules of Asylum by James Follett, broadcast by BBC Radio 4 in 1973. He also played Dibden Purlew in Getting Nowhere Fast from 2001 to 2004.

Challis is currently married to his fourth wife Carol. They married in 1995 in Brighton and once lived in the former grange house of Wigmore Abbey, Wigmore, Herefordshire. Challis has no children. He and his wife live in North Herefordshire, near Leintwardine, close to the Shropshire border.

His other television appearances include Dixon of Dock Green, The Sweeney, Doctor Who (The Seeds of Doom), Dracula, Beau Geste, Juliet Bravo, Coronation Street, Bloomers, Citizen Smith, Ever Decreasing Circles, Doctor Snuggles, Chance in a Million, The Bill, One Foot in the Grave, Open All Hours, The New Statesman, Don’t Wait Up, Soldier Soldier, Brass Eye, My Family, In Sickness and in Health, Last Of The Summer Wine, Benidorm and Heartbeat. In the 2008 series of Last of the Summer Wine he guest-starred as a fake jewel thief trying to impress the ladies.

In 2014, Challis began a theatre tour of his one-man show titled Only Fools and Boycie, which charted his life before, during and after his time as Boycie.

In 2016, Challis was cast in the role of Captain Peacock, originally played by Frank Thornton, in a remake of Are You Being Served?. The episode aired on the BBC in August 2016. In the same year he returned to the world of Doctor Who by playing Rosser in an audio play starring Tom Baker called The Trouble with Drax.

Challis has had a number of stage roles. He starred in pantomime at the Plaza Theatre in Stockport as Captain Hook in Peter Pan, a role he reprised in 2018 at the Theatre Royal, Nottingham. He also appeared in pantomime at Weston Playhouse in winter 2011–12 playing Ebenezer in Aladdin and as King Rat in Dick Whittington at the Plaza Theatre in Stockport over Christmas 2013 and New Year 2014. In 2006 he took a cameo role in BBC’s The Impressionists as Station Master Garre Saint Lézasr. He appeared alongside Christmas enthusiasts Paul Toole and Chris Elliott in the Channel 4 documentary King Of Christmas Lights, which aired on 19 December 2011, switching on the Christmas lights at Manning Close in Wells, Somerset, on 30 November. He also flicked the switch in Weston Super Mare on 1 December 2011. In 2013 Challis occasionally contributed to the Hitchhiker’s Guide To The Galaxy Live Tour as the narrator.