Bitlings aren't trapped inside an app you have to go and open. Each creature gets its own transparent, borderless window that sits on your real desktop — so they walk in front of Finder, behind your browser, and around whatever you were supposed to be doing.
Each bitling has its own voice, moods, idle animation and things to say. They are not reskins of one another — Moss will not say what Cinder says, and neither of them will be quiet about it.