Fictional Character From Battlestar Galactica
The Cylons of the 1978/1980 series are not the mechanical foils seen throughout the series, but an advanced reptilian race who created the robots (who were referred to as Cylons within the show) to serve them, maintain their vast empire and to man their military forces in the face of a sudden population drop that eventually led to the Cylons' extinction — seemingly overnight. This fact is briefly mentioned in the 1978 movie-length premiere of the series (near the end of episode 2 in syndication) when Apollo relates the Cylons' origin to Boxey.
In the episode "War of the Gods", during Count Iblis's private discourse with Count Baltar, Baltar mentions that he recognizes Iblis's voice, referring to Patrick Macnee's voicing of the Imperious Leader in the opening episode/theatrical movie (Macnee also played Iblis), with Iblis countering that if that was true it must have been "transcribed" over a thousand yahren (years) ago and programmed into the mechanical body of the Imperious Leader.
The follow-up series Galactica 1980 had a two-episode arc entitled "The Night the Cylons Landed" that featured a humanoid Cylon, though unlike its successors in the post-millennial reimagining, it was not organic, but a complex mechanical construct.
The Cylons of the 2003 miniseries and 2004 Battlestar Galactica series are fundamentally different from the Cylons of the original 1978/1980 series. In the new version, the Cylons were created by humans as cybernetic workers and soldiers. As in the original series, the Cylons destroy almost the entire human civilization, chasing a few ship-borne survivors into deep space. Unlike the original series, however, the reimagined series includes twelve Cylon models that are nearly indistinguishable from human beings.
Although these human-form Cylons are the focus of the series, alongside the humanoid models there are also Centurions similar to those in the original series. Much of the Cylons' technology is based heavily on bioengineering and/or synthetic biology rather than conventional robotics. Humans often derisively refer to Cylons as "toasters," due to the resemblance of the Cylon centurions from the first Human/Cylon war (the design of which is based on that of the centurions from the original series) to "walking chrome toasters", as described by Gaius Baltar in the miniseries. The humanoid models are referred to as "skin-jobs" to differentiate the two variants.