Doug continued to make guest appearances until his death in April 2016, with his storylines mostly focusing on the progression of his Alzheimer's and how it affects him and his family.

The Willis family were created following a period of poor ratings in Sydney, a cast "shuffle", and a newly hired producer Margaret Slarke.

[6] In his book, The Who's Who of Soap Operas, Anthony Haywood described Doug as being a "rugged and down-to-earth builder", who is usually easy-going but does have "an awful temper" when provoked.

[6] He was "baffled" by Gaby's (Rachel Blakely) rebellious nature, while Cody (Amelia Frid), his youngest child, was the apple of his eye and often came to him with her problems instead of her mother.

[7] In his fictional backstory, Doug accepted a dare to travel naked across town in a tax driven by Pam Beresford (Sue Jones).

[9] Doug devotes his time to his construction business, while Pam's job as a district nurse gives her increasing independence.

Meanwhile, Doug attracts the unwelcome attentions of the lonely and "dogged" Jill Weir (Lyn Semler), who is dealing with the death of her son, Ross (Che Broadbent).

[9] When Pam refuses to accompany Doug on a work trip, he mistakenly believes that she wants to spend more time with Jim, with whom he suspects she is having "a torrid affair".

[10] Another Inside Soap columnist questioned whether the Willis marriage would survive and Jones told them: "I think it's worth saving.

"[15] On the orders of his new boss, Mr Baker (Fred Barker), Doug had to take on his nephew – Terry (Adam McInnes) – a lazy "good-for-nothing", who had no interest in the business.

[17] Donovan quit Neighbours to return to the stage, after securing a role in a musical production of Peter Pan in Britain.

[19] On 14 April 2005, Kris Green from Digital Spy confirmed that Donovan would be reprising his role for a guest appearance during the serial's 20th anniversary celebrations, which were broadcast in July.

[22] During his stay with Brad, Doug got the chance to teach his grandson Josh (Harley Bonner) some practical skills and "the ropes of the building trade".

"[24] He later stated "I really do think Jason (Herbison), the producer, the company itself, has taken an enormous step in introducing a character who has the early signs of Alzheimer's or dementia.

"[4] The actor was asked to be an ambassador for Alzheimer's Australia as a result of the storyline,[24] which he accepted as he had first hand experience with the condition and wanted to help.

[29] Doug moves in with Brad and partner Lauren Turner (Kate Kendall), marking the first time he had lived on Ramsay Street in 21 years.

[29] Due to his condition, Doug quickly loses his temper with Lauren and seeks out Brad's wife Terese Willis (Rebekah Elmaloglou).

[30] In his exit storyline, Doug collapses shortly after witnessing Brad reunite with his estranged son Ned Willis (Ben Hall).

[32] Donovan reprised the role for the finale episode of Neighbours in July 2022, appearing as a ghost watching Terese and with Paul at a street party.

When Doug does some work on Number 28 Ramsay Street in preparation for a sale, he decides to purchase the house and the family move to Erinsborough.

Doug and Pam's financial troubles continue due to Cody's student exchange fees and them having to bail Brad out of jail.

Gaby gives birth to a son, Zac (Jay Callahan), who is named after Doug's grandfather and she leaves to run a hotel in Darwin.

Doug returns with Philip Martin (Ian Rawlings) and they sneak into Number 22 and paint a beard onto a sleeping Lou's face.

Josh also becomes concerned when Doug messes up a couple of jobs, leaves the yard unattended and gives Imogen (Ariel Kaplan) alcoholic ginger beer by mistake.

Doug returns a few months later to support Josh ahead of his court case for punching Chris Pappas (James Mason).

Doug's condition continues to deteriorate and his family consider putting him in a nursing home but decide to hire Nene Williams (Ally Fowler) to care for him.

Six years later, Susan imagines Doug talking with Harold Bishop (Ian Smith) during a Ramsay Street party.

A writer for the BBC's official Neighbours website stated that Doug's most notable moment was "Having an affair with Jill Weir.

[37] Barbara Toner from the newspaper criticised the actor's delivery of dialogue in scenes, stating that "no-one could make a three-word sentence last longer than Terence Donovan.

"[38] Bill Ferguson of the East Kilbride News agreed with Toner, stating "Duuuug speaks with looong vowels through tissssue paper, wears a perpetual grin (must have a sore face) and has had a wee bit of playing away from home when he 'phoned from a convention hotel and, because Big Jim answered the 'phone, assumed there was some hanky panky between him and Duuuug's wife..."[39] During her feature on Neighbours, Anna Pickard from The Guardian tried to choose the characters she would be most starstruck by if she met them.