The game's soundtrack was composed by Masato Nakamura of the band Dreams Come True. A group of fifteen started working on Sonic the Hedgehog (16-bit), and renamed themselves Sonic Team. Eventually, Naoto Ōshima's spiky hedgehog, initially codenamed "Mr Needlemouse", was chosen as the new mascot. Several character designs were submitted by its AM8 research & development department, including an armadillo (who was later developed into Mighty the Armadillo), a dog, an over-sized Theodore Roosevelt in pyjamas (which would later be the basis of Doctor Eggman's design), and a rabbit (intended to use its extendable ears to collect objects these aspects were later incorporated into Ristar). In April 1990, Sega requested a game capable of selling over one million copies and a character to replace Alex Kidd as the company's mascot.