wordplay

You treat the two needles as one really BIG needle. It's no different from casting on with one needle. Once the stitches are all on, you pull the extra needle out, leaving the stitches on the one remaining needle, as usual. And no, as long as you're casting on pretty tightly anyway, it doesn't make things look funny or cause any problems - I do it all the time. Another option is to cast on with two slightly smaller needles, ie if your pattern asks for size 6 needles, cast on with two size 4-5s, pulling out the extra needle afterwards, as above, but use the regular size 6s for the actual knitting from that point on.