Introduction

The LEGO® Fan Universe is, as the name indicates, a fan-created universe based on the popular Danish construction toy. The core goal of this universe is to combine the original themes into a cohesive setting for countless stories, taking a different path than The LEGO Movie. Inspiration is taken from various sources; themes, video games, and films. Some of the greatest influences are described below, with their sources indicated as superscript.

Imagination

A core element of the universe is 'Imagination', which is the magic system of LEGO.^{LEGO Universe} Similar to the Force, it created life and is what binds the universe together. Imagination exists everywhere and can create virtually anything from nothing. It was first used by the mythical First Builders, who created the Imagination Nexus. The Nexus absorbed the raw Imagination and transformed it into Pure Imagination. The First Builders harnessed Pure Imagination to build their civilization, and is what all current forms of life use. Raw Imagination is dangerous as it flows without restraint; chaotic and uncontrolled.
Living beings possess a 'Creation Spark', which represents their life essence and gives them the ability to tap into Imagination.^{The Adventures of Clutch Powers} Minifigures cannot 'die' by being 'smashed' or otherwise disassembled, unless their Creation Spark is extinguished. Extinguishing a Creation Spark is not easy though, and usually requires powerful magic or technology. 'Deconstruction' is a method that drains LEGO bricks of all their Imagination, which prevents them from being assembled.^{LEGO Batman 2} This method can therefore also extinguish a Creation Spark.

Themes

The Fan Universe uses the original 'core' LEGO themes as a foundation; Town/City, Castle, and Space, in addition to Pirates and Adventurers.
For clarity and worldbuilding, LEGO themes are sorted in three categories:

1. Setting: Setting themes are designed purely to provide a generic backdrop based on a specific era or location. Examples are City, Castle, Space, and Pirates.
2. Narrative: Narrative themes tend to focus on storytelling, often using a very specific and unique setting. Examples are Alpha Team, Rock Raiders, and Agents.
3. Licensed: Licensed themes are not original to LEGO but based on existing IPs. Examples are Star Wars, Harry Potter, and Marvel/DC Super Heroes. These themes are excluded from the Fan Universe, but may appear as part of the multiverse.

Aside from these three types of themes, they may also obviously be combined to different degrees. Rock Raiders for example provides both a setting (alien planet) and an overall plot (lost in a distant galaxy without power). But for the sake of worldbuilding, I categorize each theme by their most prominent role.

Worlds & realms

The LEGO universe is similar to ours, with galaxies, stars, and planets. There is an equivalent of Earth, which consists of multiple realms based on the core themes of City, Castle, Pirates, and Adventurers. But many other worlds exist, each focused on a distinct standalone theme, including, but not limited to, Ninjago, Bionicle, and the fantasy-oriented 2007 Castle theme.
Earth is the most diverse world, but its realms are mostly focused on the more mundane core themes. Some elements of fantasy and science fiction are used, notably with the Alpha Team, Agents, Adventurers, and Pharaoh's Quest themes, but these are not as significant compared to the more fantasy and science fiction oriented themes such as Space Police and the 2007 Castle theme. The notable difference is that the former are combined with the core themes while the latter are used independently.