This is Bubbles, she's a slime pony with a heart of gold and slime that's not only edible, but tastes like watermelon and works as an antibacterial soap. The cutiemark she has shows that due to her soapy slime trails she loves to clean and using her magic (Which is how she changes her soap like properties through the various kinds of cleaners) cleans messes for a living... mainly places to stay.

She's very naive especially since even though she appears to be a full grown pony mare, she's actually only three years old as slimes maturity is completely independent on their growth which is managed by feeding on their respective source and staying hydrated.

The Source, is the term used to describe what a slime needs to consume to grow lagers, for a Slime made of watermelon flavored edible soap this is bacteria... and cookies, she really... really loves cookies.