Bill Stickers is innocent
Play on words, based on 'Bill Stickers...' notices.
In the UK in the 1960s an attempt was made to reduce fly posting (the illegal pasting up of posters) and warning notices were put up with the legend 'Bill Stickers Will Be Prosecuted'. Waggish fly posters responded with 'Bill Stickers is Innocent' notices.
The joke wasn't new in the 1960s though. In a New York newspaper The Olean Herald, 1884, there's a piece reprinted from the London Graphic:
"A countryman named William Stickers, flying to London to escape from rural justice, was appalled at reading on a wall: 'Bill Stickers Beware!' He went a little further, but reading again, 'Bill Stickers will be punished with the utmost rigour of the law,' gave himself up for lost and surrendered."
This tale, which is just a joke of course and not a verbatim report, appeared in various forms in newspapers in the 1880s.