1. "What's a tickle look like?" That was the question which launched the series, asked by a young Adam Hargreaves of his dad Roger. Inspired, Roger created the first Mr Men book, Mr Tickle, in 1971. Another five books came out that year.
2. With some alternate titles, special editions and foreign-language only versions it can be hard to keep track, but there were a classic 48 characters and 42 Little Misses. Our favourites are 1972's Mr Daydream, 1976's Mr Dizzy and 1981's Little Miss Naughty.
3. The Mr Men books cost just 15p when they were first released. A brand new Mr Tickle will now set you back a whopping £2.50! But we recommend buying a complete collection for extra value and fab box to keep them all in order on your shelf.
4. When Roger Hargreaves passed away in 1988, his son Adam took over the series. He wrote four books based on characters developed by his dad (Mr Brave, Mr Grumble, Mr Perfect and Mr Cheerful), before making his own mark with 2003's Mr Cool.
5. The Mr Men first made it to the telly in 1975, with the help of Arthur 'Captain Mainwaring' Lowe. He narrated the stories and also voiced all the famous characters. They came back in 1983 and 1995 before returning in 2008 with two runs of The Mr Men Show. The US cartoons created brand new characters Little Miss Daredevil and Little Miss Calamity, while Little Misses Stubborn and Scatterbrain had sex-changes to Misters.
Watch the classic Mr Tickle narrated by Arthur Lowe below:
6. Perhaps to prove that we really are two nations divided by a common language, the Mr Men Show was dubbed from American English into British English, with the unexplained exceptions of Mr Scatterbrain and Mr Rude. In 2007, stars including John Simm, Joanna Lumley, Tony Robinson and Ben Shephard voiced Mr Men and Little Miss characters for a number of charity podcasts.
7. Most of the books are based around a single character and are set in places like Happyland, Nonsenseland and so on. In the new TV shows, all the Mr Men and Little Misses live together in the town of Dillydale, created by producer Peggy Regan. She has been given the honorary title of The Mayor of Dillydale!
8. In 2001, the Sunday Times launched a competition to celebrate the 30th anniversary of the series. 8-year-old Gemma Almond won, and her creation Mr Cheeky was sold in WH Smith, with proceeds going to a leukaemia charity. A Little Miss Stella book was published by Adam Hargreaves in 2006 for Stella McCartney to use as fashion show invitations, making her the first real-life person to directly inspire one of the characters.
Watch an unhappy Mr Happy in a Specsavers advert below:
9. The rights to the series were sold by Roger's widow Christine in 2004 for a whopping £28 million, making her Little Ms Loaded!
10. Around 120 million Mr Men and Little Miss books have been sold worldwide since 1971 and one is now bought every 2.5 seconds. The man who started it all off - Mr Tickle - remains the most popular.