Play virus levels 5, 10, or 15 at medium or high speeds. Wait at the intermission screen that features three viruses in a tree. A bonus object will appear at the top of the screen. A different object will appear depending on which level and speed is currently being played.

After completing level 20 on medium or high speed, an object will fly above the little viruses on the tree.

The viruses are Red, Yellow, and Blue and are placed in random order in the bottle, when you start.

Blue/Blue: Eliminates Blue Viruses
Red/Red: Eliminate Red Viruses.
Yellow/Yellow: Eliminate Yellow Viruses.
Red /Blue: Eliminate Red, Blue, or both.
Red/Yellow: Eliminate Red, Yellow ,or both.
Blue/Yellow: Eliminate Blue, Yellow or both.