There are several entities named "Bubble". For instance, Bubble Cash is a legitimate app with over 103,000 app store reviews and an average rating of 4.6 out of 5 stars. It's developed by Papaya Gaming, one of the top mobile gaming companies in the world. However, Bubble Arena has received negative reviews, with users reporting that it's impossible to cash out or that payments don't credit. Therefore, the legitimacy of "Bubble" depends on the specific entity in question. If referring to another "Bubble", please provide more details.