Some stars are obsessed with their hair or their waistline or their bust size.

But Sylvester Stallone appears to be obsessed with maintaining his tough guy appearance.

The 66-year-old action movie star made a special appointment at the MD tattoo studio in Hollywood on Sunday for a new piece of body art, even though the parlour is usually closed that day.

The Expendables actor arrived at the studio in the morning wearing a black velour Puma jumpsuit and black tennis shoes.

Inside Stallone stripped off his shirt, maintaining his trademark pouty-lipped, tough-guy expression he's become known for while the tattoo artist taped plastic wrap over his existing tattoos and prepared to get to work.

The Cliffhanger star has been sporting tattoos over his arms and back for many years now, a different look and style than the all-American Rocky character that turned him into an international film icon in the late 1970's.

However, many of the tattoos Stallone has gotten in recent years are to cover scars that he has accumulated over his years in action films, he claims, rather than a mere stylistic choice.

'I have all kinds of chest injuries; I tore my vein during 'Rocky II' and had 60 stitches,' Stallone told contactmusic.com in early February while doing press for his latest film Bullet to the Head. 

'If you've seen 'ROCKY BALBOA', you'll know how bad they look. It got worse and worse, and people were saying, 'Urgh, has he got varicose veins?' So I thought, 'f**k it', and covered them with a tattoo of my wife.'

This first tattoo, a portrait of Stallone's third wife model Jennifer Flavin, was subsequently surrounded by three roses representing their three daughters Sophia, Sistene and Scarlet.

After that, the Rambo star said he added a skull tattoo and before he knew it, his body became a mural.

Tattoos now cover his upper back, shoulders and chest in a wide variety of intricate designs.

They are featured in all of the Expendables films and will most likely be prominent in the two action features starring Stallone due out later this year.