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In the late 1990's, Jeff Marx and Bobby Lopez produced a spec script for a Muppet feature film called Kermit, Prince of Denmark. Like The Muppet Christmas Carol and Muppet Treasure Island before it, this was a loose adaptation of an earlier work, this time William Shakespeare's play Hamlet. In the script, Kermit accidentally travels to Denmark, where he turns out to be the exact double of Prince Hamlet and is frequently mistaken for him. The project was conceived as a musical, with Marx and Lopez writing eight songs for the project as well.
Marx and Lopez won the 2000 Kleban Award, a $150,000 endowment to encourage musical theatre writers, for the script (they tied with four other writing teams and hence received $30,000). The script was subsequently sent to the Jim Henson Company, but according to Jeff Marx: "[Brian Henson] said he wasn't interested, and that was that."
Marx and Lopez would go on to write the acclaimed Broadway smash Avenue Q, which in part parodies characters from Sesame Street. Marx said that the experience of being rejected by Henson made them determined not to write for other people's characters.