The LEGO Maniac is an iconic LEGO character used by the LEGO theme in instructions and commercials. In commercials, the character was shown building things and playing with them, accompanied by a song about their LEGO mania (nearly the same in every case, except that they had a few variations for different themes). LEGO originally had their LEGO Maniac named Zach/Zack, but when an imitator made their "sets" under the name of Zaks, LEGO changed the name to Jack to avoid unintentionally advertising for this fake. They changed it back to Zach later. Zach has been played by three different people. The last LEGO Maniac commercials aired in 1994. In 1990-1994, the LEGO Maniac advertised Blacktron Future Generation, Ice Planet 2002, Nautica, Flight (Town), Pirates and Islanders, among other themes.
In LEGO set instructions for some older themes, the LEGO Maniac (a cartoon individual) was shown "playing" or "adventuring" within the theme/set.