In the Famicom version of Rockman 2, some of the English letters have some typo errors including Pass Word being spaced out, and at the Credits including some words like Caracter Designer and Sound Prgrammer which was later corrected in the NES version to Password which is combined together, Character Designer, Sound Programmer.
When we first see Dr. Wily's castle, his saucer flies toward the castle, and we hear the appropriate "saucer beep" sound effects. But in the subsequent exterior shots of the castle, we still hear the saucer noise, even though the saucer is nowhere to be seen.