From the Super Mario Wiki, the Mario encyclopedia
The Shakespeare Bust is an item in the NES, SNES and PC releases of Mario is Missing!. It is a bust of William Shakespeare that was being held in Westminster Abbey that is stolen by a Koopa Troopa under Bowser's orders. When Luigi visits London and reclaims it, he questions the various locals about it. After gathering enough information, he takes it to the information booth at Westminster Abbey to answer various questions about the bust. The Abbey is then reopened to the public.