'The Hurt''s arpeggio (heard at 0:26) also turns up at 0:22 of 'Casino Night Zone 2Player' in Sonic 2.
Marble Zone sounds an awful lot like The Jacksons' 'The Hurt' as well as Andy Williams's 'Music to Watch Girls By'.The opening melody of Green Hill Zone is remarkably similar to the chorus of Billy Joel's 'Big Shot'.