The girls, who were in the city attending New York Fashion Week, relied on each other for moral support as they got the inkings done.
While Cara paid tribute to her mother Pandora with an etching of her name in fancy script, Rita went for a more daring choice and chose a ten-inch tattoo of a '50s style Alberto Vargas pin up girl on her ribcage.
The R.I.P. singer revealed the tattoo in a snapshot on Instagram, where Rita is pictured posing topless, next to the caption, "Say hello to my new little friend Rosetta...thank you @bangbang she's beautiful."
"The tattoo is on her right ribcage. It's big! When she's standing it's about seven inches tall, but when she's laying down it's about ten inches, plus," an insider at Bang Bang told E! News, and added that the skin art took five hours to complete.
Cara kept her best friend entertained and distracted from the pain, by dressing up in a hamburger costume.
"She just pulled it out of her purse, put it on, and was like, "just me and my hamburger, what, what!" She's hilarious. She's genuinely fun, one of my favourite people," said the tattoo artist.
Just last week Cara revealed to her fans on Twitter that she was considering getting another etching done of her favourite food.
"Should I get a tattoo of bacon or cheese??" asked the model of the moment.