Play as Monica
To play as Monica from the stage "Below Freezing Point" you must first complete the stage with any character. Once done, go to the "Collection" option at the main menu and choose "Costumes". Her costume costs 5,000 points, Once unlocked you can play as Monica on any stage. Note: This is one of Alyssa's costumes; Monica will have Alyssa's voice effect.
Play as fire fighter or policeman
To play as a fire fighter or policeman, complete the stages "Outbreak" and "Hell Fire" with any character. Once done, go to the "Collection" option at the main menu and choose "Costumes". Both of those costumes cost 5,000 points. After unlocking them, they can be used on any stage. Note: They are Kevin and Mark's other costumes. When playing as either a fire fighter or policeman, they will have Kevin and Mark's storylines and voice effects.