LEGO, from the Danish words "leg godt" or "play well," is a brand of molded plastic bricks and other components that fit together to create an endless variety of structures and figures. The original patent on the LEGO bricks has expired, but LEGO now patents each individual set it sells. As such, other companies can create compatible bricks without violating the trademark.
Until 1995, Tyco sold a basic brick bucket containing 500 or 1,000 pieces that were compatible with LEGO bricks. They were available primarily in contrasting colors including charcoal gray and olive green, neon yellow, hot pink, violet, pastels and sky blue. These blocks resemble LEGO bricks, but the pegs on top say "Tyco" and the colors are not the same as LEGO bricks from that era. These bricks were marketed as superblocks. Tyco also released Duplo-compatible bricks.
Introduced by a company called Ritvik, Mini-Micro Blocks were released alongside Mega-Micro Blocks to be compatible with LEGO blocks. These blocks come in 1,000-piece containers, with the most common pieces being 1 x 2, 2 x 2 and 2 x 4 bricks. Although the Mini-Micro Blocks offer a tight fit, they are fully compatible with LEGO bricks. Mega-Micro Blocks are not LEGO compatible as their knobs are shorter and they do not offer the same level of friction for connecting blocks.
Tandem Bricks is a California-based company offering LEGO-compatible building bricks. The largest available brick is 2 x 4 with a full height and is compatible with 2 x 4 LEGO bricks. Many Tandem Bricks are 1 x 3 flat pieces that are the same height as the 1 x 3 LEGO bricks. Tandem bricks offer similar colors as LEGO, but with a larger proportion of green bricks and gray flat bricks. The quality of these bricks is similar to LEGO, but the pieces do not fit together as well.
A number of LEGO-compatible building blocks have been marketed through the years with similar names. These LEGO "clones" do not typically survive for long on the market. Some examples of LEGO building block clones are ELGO, PEDLO and Blocks. Most of these blocks are almost perfectly compatible with LEGO, except for PEDLO blocks, which were taller than LEGO blocks and not fully compatible.