Between 1968 and 1973 Nicholas Cartoons produced a series of public information films for the Central Office of Information starring a dim-witted Northern couple named Joe and Petunia. Voiced originally by Peter Hawkins and Wendy Craig (Craig was eventually replaced by Brigit Forsyth), the characters appeared in four films: Coastguard in 1968, Water Safety (Flags) in 1970, Acceptance of the Country Code in 1971 and Worn Tyres in 1973. Denis Gifford lists the director of Flags as Nicholas Spargo, of Willo the Wisp fame; I'm assuming he directed the entire series.
Coastguard (analysed in this BBC article) sees the two characters at the seaside, where they catch sight of a distressed boatman. Mistaking his cries of help for friendly waves, they cheerily wave back - until Joe looks through his binoculars to get a better look at the man's speech balloon.
In Water Safety (Flags) Joe is itching to go for a swim after seeing a mermaid through his binoculars, but Petunia - now serving as a straight partner - cautions him against swimming where red flags or warning signs are present. She allows him to go for a dip where there's a coastguard, but the coastguard makes off with the mermaid himself.
In Acceptance of the Country Code the couple drop litter, traipse through a cornfield and let their dog hassle some sheep; they then see a farmer with a purple face ("I expect it's all that sun in the open air") dancing a country dance. Detecting that he isn't happy, the two vacate the scene ("it can't be anything we've done!") The film has its own Screenonline article, discussing the social background to the short.
And finally there's Worn Tyres, in which Joe and Petunia are out for a drive. Petunia sees a sign reading "Worn Tyres Kill" and repeatedly asks Joe if he's checked their tyres. "Not worn, Petunia, they're a bit smooth", he reassures her. The car then skids off the road and crashes into a tree, a which point the film cuts to an identically-composed photograph of a crashed car. Their first lines from the film echo on the soundtrack ("nice view from up here, Petunia") while text reading "Worn Tyres Kill" appears on the screen.
As this was the last film in the series, it would appear that Joe and Petunia are dead. The characters have their own Wikipedia article which comments on their apparent demise:
They appeared in four films which ran between 1968 and 1973, and they became popular so quickly that it was decided to kill them off in the last one in order to prevent public demand for their reappearance.The article does not provide a source for this claim, and so it should be taken with a grain of salt, but it certainly sounds plausible. Another unsourced tidbit is that there were in fact five films in the series: "They also appeared in a much earlier public information film which showed them learning to use a pelican crossing, but it is noticeably different from the others in the series."
I haven't been able to verify this. The article could be making a muddled reference to Pelican Motorist, a film featuring a vaguely similar (but far more competent) couple who are not named; however, this film was released one year after Joe and Petunia had already appeared in Coastguard. Denis Gifford's filmography - restricted to animation released in cinemas - lists a 1971 cartoon titled simply Joe & Petunia; this is presumably Acceptance of the Country Code.
Joe and Petunia may have passed away in 1973, but like the protagonists of a solar myth they did not stay dead forever. In 2006 a revised version of Coastguard hit our screens, with Joe and Petuinia now sporting twenty-first century fashion accessories, marking the Central Office of Information's sixtieth anniversary.