DUPLO is a theme and a subline intended for children aged 1-5 years old, and was introduced as a brand in the year of 1975, though the name and the blocks had already been around since 1969. The three forms of minifigures, or DUPLO figures are more sizable and stable,  and the blocks are about twice the length, width, and height of their equivalent System brick and half the length of a QUATRO brick. It can be noted that DUPLO is compatible with normal System bricks, but only with 2x2s and further because it's too big for 1x1 and 1x2x3 bricks.
The first DUPLO bricks and the name DUPLO appeared first in the year 1969. There were originally four colours: Red, Yellow, Blue, and White. They were designed to connect more with System bricks than the newer DUPLO bricks of recent years. The bricks were 18 times larger than a regular system brick. They were released in sets 510, and 511, both with System bricks. They were considered to be System-Duplo sets, aimed at younger children. This was the beginning of the LEGO Group's products for the younger market. Two more sets were introduced the next year, adding new blue and red wheel plates.
The sets were designed for 1 to 2-year-olds, but were continued to be mixed with System blocks.  In 1972, the first 2x2 studded brick was introduced.
When DUPLO/Pre-School sets were introduced in their final form in 1969, the first DUPLO sets had a green LEGO logo. This logo was short lived, and by 1971 new DUPLO sets were introduced that used the red LEGO logo, and the text 'DUPLO' in green on the box'.
In 1975 DUPLO became an independent theme, with five sets made up exclusively of DUPLO bricks. In 1977, the decision was taken to rename DUPLO Preschool. In the Preschool range, new DUPLO bricks were introduced, including arches and the first DUPLO figures, which did not have movable limbs. In 1979, the theme was returned to the name of DUPLO, and received its logo, a rabbit designed in a style similar to PRIMO's elephant. 
In 1983, DUPLO Figures were similar to their current design, with moveable limbs. They were more like larger minifigures than their predecessor, minus the ability to be taken apart, due to their target audience being young children. It also saw the first DUPLO Trains, and the DUPLO Baby series.
In 1993, a grey-train rail system, 4.5v arrived. Since then there have been two others. Only two motorized sets were released in the DUPLO theme. In 1995, DUPLO Primo was launched. (DUPLO Baby in America) On the first of January in 1997, Primo and DUPLO were officially renamed LEGO DUPLO and LEGO PRIMO. 1999 saw licensed sets introduced to DUPLO, with Winnie the Pooh
Explore and licensed success (2000 to present)
In 2002, the name was once again dropped, and the theme combined with LEGO Baby to form Explore, which tried to encourage children to explore life. In late 2004, however, Explore ended and DUPLO was once again back.
In 2010, a deal with Disney saw the return of Disney characters in DUPLO sets, unseen since Mickey Mouse. Toy Story and Disney Cars all saw several sets released. Disney Cars has been released in DUPLO and Lego sets.
Further more, in 2011, a second line of Winnie the Pooh sets was released, in 2012 Disney Princess was released, in 2013 Mickey Mouse & Friends, Planes and Jake and the Never Land Pirates were released, in 2014 DC Universe will be released.
With the success of the Friends line, DUPLO added more female characters and girl based sets in 2012, 2013 and 2014.
Themes of DUPLO
Dacta DUPLO (1975 - 1977, 1979 - 2002, 2004 - present)
Dacta or Educational DUPLO sets are those released under LEGO's educational brand, Dacta. They are often designed for schools and include things like LEGO tables.
Dacta DUPLO Subthemes
- DUPLO Basic (Dacta)
- DUPLO Community
- Dino (Dacta)
- DUPLO Farm (Dacta)
- DUPLO Learning
- DUPLO Mosaic
- DUPLO Playhouse (Dacta)
- DUPLO Rattles (Dacta)
- DUPLO Supplementary (Dacta)
- DUPLO Toolo (Dacta)
- DUPLO Train (Dacta)
- DUPLO Zoo (Dacta)
- Explore (Dacta)
Town (1978) - (2003)
DUPLO Town sets were introduced in 1978. The sets ranged from fire and police to circus and race related sets. From 2004 The LEGO Group has used the name LEGO Ville for all DUPLO Town related sets.
Playhouse (1979-1980, 1982,1986, 1988, 1990-1998, 2000-2001, 2004)
Playhouse sets were introduced in 1979. The sets cover scenes from houses or single rooms to furniture sets for DUPLO Figures.
Train (1983 - 2002, 2005 - present)
DUPLO Train started in 1983 and is still active today. Thomas and Friends sets can be considered part of this theme. There have been three track varieties so far.
Baby (1983 - 1994)
Toolo (1992 - 1999)
In Toolo, the pieces where held joined together using tools, like a screwdriver. 14 sets were released. A car based version, Action Wheelers, was released after Toolo ended.
Primo (1995 - 1996)
DUPLO Western (1998)
DUPLO Western sets were released in 1998. Eleven sets were released in this subtheme.
Dinosaurs (1998 - 1999)
A prehistoric based theme, Dinosaurs ran for two years. This theme was continued as Dino ten years later. Included were Dinosaurs and Cavemen.
Little Forest Friends (1999 - 2000)
Little Forest Friends was based on people who lived in a forest and what goes on in their lives. It contained twelve sets, including a story book.
Winnie the Pooh (1999 - 2001, 2011)
Winnie the Pooh was the first LEGO and DUPLO licensed theme based on the Winnie the Pooh stories by AA Milne and the media based on them with figures such as Pooh , Piglet and Tigger.
Action Wheelers (2000 - 2001)
Bob the Builder (2001 - 2002, 2004 - 2009)
One of the longest running licensed themes, Bob the Builder is based on the British children's TV show of the same name. It mainly featured the vehicles from the show. It became part of Explore when it was formed in 2002 and when DUPLO returned, Bob the Builder also returned with it.
Dolls was a 2001 attempt to get into the Doll market. There were nine regular sets available.
The theme of three sets, Zooters featured three named creatures. The theme only lasted a year.
Castle (2004 - 2008)
Two Ferrari DUPLO sets were released in 2004. They were similar to System releases.
LEGO Ville (2004 - present)
Farm (1979 - 198?, 1997-1999, 2010-present)
Thomas and Friends (2005 - 2009)
Thomas the Tank Engine and Friends is a theme based on the Thomas the Tank Engine books and TV show. It is closely related to Train.
Four sets were released in the DUPLO equivalent of Pirates. The sets mainly contained ships.
Dino was an remake of the Dinosaurs theme from ten years earlier. The theme had twenty sets featuring different types of dinosaurs and DUPLO Figures.
Toy Story (2010)
Cars (2010 - 2011)
Disney Princesses (2012-present)
Disney Princess is a Disney licensed theme based on the stories of some of the most famous princesses.
Jake and the Never Land Pirates (2013-present)
Jake and the Never Land Pirates follows Jake's pirate adventures in Neverland.
Mickey Mouse & Friends
Mickey Mouse & Friends follows the adventures of Mickey and his friends having a fun time.
Other DUPLO Related Sets
- GA06 DUPLO Memory Card Game 1
- GA08 DUPLO Little Forest Friends Counting Game
- GA12 DUPLO Toolo Memory Card Game
- GA13 DUPLO Learn and Play Look and Find Memory Card Game
- GA15 DUPLO Memory Card Game 2
Related Systems and Themes
LEGO have also made other themes aimed at the younger children market.
- System-DUPLO; the origin of the DUPLO brick was here in 1969, when it was released with System sets before DUPLO became a theme.
- PreSchool was what DUPLO became in 1977, but by 1979 it was renamed DUPLO again.
- Baby, not to be confused with the DUPLO subtheme, was released originally as DUPLO Primo in 1995. In 1997 it became independent and external of the DUPLO theme, as Primo. In 2000, it was once again renamed to Baby. In 2002, it and DUPLO formed Explore. Baby ran again from 2004 and was discontinued in 2006.
- Explore, an attempt to join together Baby and DUPLO as an all-compassing theme for younger children. With two years it was reverted back to the pre-2004 names.
- The word "DUPLO" comes from the Latin duplus, which means double referring to the size.
- An average LEGO brick is able to connect to a DUPLO brick, and an average DUPLO brick can be connected to a Quatro brick.
- The DUPLO Figure cannot be broken and rebuilt, and if they move one arm, the other arm moves too.
- DUPLO Minifigures and bricks are about twice as big as normal Minifigures and bricks.
- It's one of the longer-lived themes,as it was introduced at the first years of Lego working with bricks,and continues till present day.
- DUPLO often mistakably considered another brand, because of its extreme popularity.
- DUPLO it's the only theme that appears in Logo Quiz app.
- DUPLO Aliens made an appearance at the end of The LEGO Movie.
Notes and References
- ↑ http://www.lego.com/eng/info/default.asp?page=timeline
- ↑ http://www.lego.com/eng/info/default.asp?page=timeline4
- ↑ Catalogue 1971
- ↑ Catalogues, 1977 and 1978 show name PreSchool, 1979 DUPLO.
- ↑ The LEGO Book, DK