Although the character Stan Butler was supposed to be in his mid-30s, Reg Varney was already 52 when the series began. He wore heavy make-up so that he would appear younger. Bob Grant (Jack Harper) was only 36 but also appeared older.
In 1990 plans were announced for a new series called "Back on the Buses" to be made by Scottish Television (STV) and produced by Bryan Izzard (who had produced several episodes of the original series and directed the feature film "Holiday on the Buses".) All the original main cast appeared on the BBC Wogan chat show to promote it, although by this time, Reg Varney was 74 and Doris Hare, 85. However, due largely to financial problems, the series was never made.
Bob Grant, playing bus conductor Jack, had actually worked in real life as a bus driver in order to pay his way through RADA (the Royal Academy of Dramatic Art), although he was sacked, for crashing his bus(!)
Reg Varney was the first person in the UK to publicly use a cash point, when he was hired by Barclays Bank to publicize the first ATM available to the public.
Reg Varney wouldn't sit out his part all the way. He left the series in the final season, after episode 69 (entitled "Goodbye Stan"). So Varney wasn't in the last six episodes of this series. His absence was explained by Stan moving to the Midlands, to work in a car manufacturing factory. Inspector Blakey moved into the Butler household as a lodger, so he was promoted from a bit-player to the show's primary character. Varney did feature in the third "On the Buses" movie later on in 1973, Holiday on the Buses (1973).