Bird poop

Here's a really good OOH from India:

Little stickers of bird poop were affixed on cars saying: "The cleanest way to do a dirty job ... Aura Car Wash and + phone."  This explainer says calls went up 45%.  I wonder what kind of stickers they used.  If they used the cheap stickers, rather than a window cling, I would be majorly annoyed, since that would take a little bit of effort take off.  And Aura Car Wash just left their number where I can yell at them.