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I recently discovered the unreleased "Seatron" theme (basically an early Aquazon prototype with elements from M-tron) as I was looking around for building ideas. After some searching, I also found the unreleased Europa theme which seems to be set in the 1700s and has elements of both Castle and Pirates.

Are there other unreleased or prototype themes and sets?

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up vote 8 down vote accepted

Brickipedia (A.K.A. list unreleased sets and themes in the form of an article and category of articles. It does mention CYBOTS and Europa in addition to Seatron, although there is no guarantee that the list is complete.


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Contained action figures using both System and the first TECHNIC ball joint parts. Several prototype models were created but final versions were not made. This theme was made mainly to test the first LEGO ball joints, which would be later used three years later on the Slizer theme.


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Set in the 18th century. The most likely reason that the theme wasn't released is that it was too close to both Castle and Pirates, both very similar themes.

Seatron enter image description here

The theme would have been set on an alien planet, with underwater astronauts. Many new monorail parts and colours were made for this theme, but when Futuron's monorail failed to make money, development of Seatron stopped.

Brickipedia have a similar list for prototype sets and themes.

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