Get a picture of a cloud
Paste it on to Illustrator
Type in text
highlight text
Select/Object/All on the Same Layer
Object/Clipping Mask
Open sub layers in the Layers section
Lock image and move text around

Make a rectangle on top of the text
Give it a color
Create new layer
Move it to the bottom
Select the path the rectangle is in and move it down to layer 2 to move the rectangle behind the text.