There is one thing I noticed in the Virus prototype version of Dr. Mario: the Intermission tune heard in Dr. Mario (after completing levels 5, 10, 15 and 20 on Medium or High) that is heard in the prototype after winning (or losing) a 2-player game (where the menu screen's BGM is the Nintendo World Championship '90 theme) isn't the finished version (again, this is what to expect in a prototype). In this case, it just plays the first version of the main melody over again.

The Dr. Mario version adds a flourish to the descending backbeat at the end of the third bar when heard for the second time, and after the main melody starts again the third time, the small flourishes before the second and third bars of the song are omitted, and the song just plays this entire version of the melody from here on.

~Ben