I’ve been to cloudbase several times, and flown into clouds. But I’ve never seen these types of clouds.
Cumulus Pixar
These clouds are designed by the people from Pixar. And they did a great job.
Look also at their Cumulonimbus. Thunder comes when clouds are angry and rain starts when they are sad.
angry
sad
I can’t find a legal copy of the movie ‘Partly cloudy’ by Pixar. But here is a link. Enjoy it. (sorry, I can’t get the video embedded in the right way. ;-()