Homestar Runner is a Flash animated Internet cartoon. It mixes surreal humor with references to 1980s and 1990s pop culture, notably video games, classic television and popular music. Originally conceived as a parody of what the authors considered to be the surplus of low-quality picture books written for children, the site mostly caters towards young adults. Most of the site's traffic comes from the United States; events in the cartoon itself usually take place in Free Country, USA. The cartoons are nominally centered on Homestar Runner. However, the series entitled Strong Bad Email, in which another main character, Strong Bad, answers emails from viewers, is the most popular and prominent feature of the site. While Homestar and Strong Bad are the main characters, the site has grown to encompass dozens of other characters over the years. The site is one of the most popular Flash cartoons on the Internet and is notable for its refusal to sell advertising space (the creators pay for everything through merchandise sales, which includes a line of T-shirts). It grew in popularity largely through word of mouth.