Curly Wurly is a brand of chocolate bar currently manufactured by Cadbury UK and sold in Australia, Belgium, Canada, Germany, Ireland, Malta, The Netherlands, New Zealand, Portugal, Romania, South Africa, Malaysia, U.A.E and the United Kingdom. It was launched in the UK in 1970. Its shape resembles two flattened, intertwined serpentine strings. The bar is made of chocolate-coated caramel.
This design was created by David John Parfitt, a long-serving research confectioner based at the Bournville factory, while he was experimenting with some surplus toffee from another piece of work. It was launched around 1970. 
Also available are "Curly Wurly Squirlies," which come in a bag and are just the cross beams of the ladder. This design was created by Charlie Simmonds, a worker and apprentice at Cadbury.
Implementing the design was difficult originally since the nozzles used to extrude the toffee would frequently jam with each other when the toffee strands touched as the middle one moved back and forth to create the pattern. This problem was solved by a mechanical engineer by the name of William Harris.
The Curly Wurly Machine was originally designed by Bill Harris, then redesigned in 1982 by Tony Wright at Cadbury's Bournville under contract from Harvey Design Company. His brief was to produce 3 times the amount of "ropes" from 8 to 24. The machine was known as a 24 rope extruder.The design office manager at the time was one Arthur Musson. Improved design of the nozzle heating system (borrowed from the injection moulding industry) meant for better and consistent flow.
The UK TV adverts for Curly Wurly in the 1970s featured comedy actor Terry Scott as the schoolboy character he'd played on the novelty record "My Brother". His catchphrase was "Hands off my Curly Wurly!".
Different versions of the chocolate have been released in other countries. A French version of the Curly Wurly was available in the 1970s and early 1980s under the name "3 Mousquetaires". A Canadian version of the Curly Wurly, known as the "Wig Wag", was available in the 1970s. A U.S. version of the Curly Wurly, known as the "Marathon", was available in the 1970s and 1980s. The German versions were called "3 Musketiers" and "Leckerschmecker". A Swedish version of the Curly Wurly, known as the "Loop", was released in 2011 under the Swedish brand Marabou (also owned by Kraft). Cadbury also marketed a U.S. version of the Curly Wurly itself in the 1970s.
Until October 2010, Curly Wurlys were produced in the Keynsham plant in Somerset, UK; however, production has now transferred to Cadbury's new plant in Skarbimierz, Poland. Labels for these products do not state a country of origin, instead stating "Made in the EU under licence from Cadbury UK Ltd"