I agree with visser101; tight clothes can be morphed, and what is a tattoo but outside materials placed under the skin? It should be easier to morph with if anything, because it is under the skin instead of on top of it. As far as scars, tattoos do scar the skin, but that's not what makes the tattoo; it's the ink
As far as what Shark said, there are a million things like that you could question. If I cut my fingernails, will morphing remember that? What about hair? If someone took growth hormone as a teenager and grew three more inches than they would have normally by their DNA, then morphed, would they return to a body that was three inches shorter? What about food? If an elephant was morphed, then a massive amount of food consumed, would the large contents of the stomach cause the human to burst upon demorphing? If a person ate a cheeseburger, then morphed fly, why wouldn't they explode? If food isn't transferred, why don't morphs starve? For instance, Jake uses the tiger for uncounted hours in total, yet he never eats as a tiger; does the tiger ever get hungry? Also, when a person is in the later stages of starvation, the body literally consumes itself, going as far as breaking apart muscles to use the proteins for energy. If tissue is regenerated, could a person technically survive forever without food by remorphing to recover tissues? It would be painful, but by this logic it should be possible. When a person is injured, they recover when morphed. But consider a massive loss of flesh like Terenia said, such as loss of a leg. When remorphed and recovered, where did the mass for the leg come from? It can't be taken from other large morphs otherwise they would be missing parts, and due to the law of conservation of mass it cannot be spontaneously created, so where did it come from? There are so many questions and inconsistencies about morphing and it could be discussed endlessly.
Is there a thread somewhere to discuss all the flaws, possibilities, and questions of morphing? I'm pretty sure there's one someplace about how age is determined from the DNA.