You may however be able to get different legitimate instructions than originally intended by jumping to an address in the middle of a multi-byte instruction that happens to decode into a useful series of operations. It follows that there are more usable "returns" in a body of code than just those written in the original source.
There are a multiple usable "returns" in functions because "return" is just "pop" then "jump", so a block that has the effect of manipulating the stack and then transferring control can often be used to the same effect as a return.
on 32-bit x86 the RET instructions are 0xC3 and 0xCB. Any other instruction containing these bytes can be subverted into a return if you can make the processor read the preceding instructions from the wrong starting point.
Sure; the authors in the Roemer paper found a couple of those. The best place to get a sense of how this works is the "Gadget Catalog" section of that paper.
