Time and time again I hear about people who would addition for a role outside of their comfort zone and get the job. What's less common is for people to audition even though their look may not match the desired look in the listing. However uncommon this is, it DOES happen. But maybe, just maybe, the reason why it doesn't happen more often is because we doubt that we can pull it off.
I'm not saying anything radical here. If the breakdown is for a 6 foot tall man in his 50's and you're a 5 foot tall young woman, the odds are that drawing a beard on your face may not do much. But keep your options open, after all acting is what we do. That's what the auditions are for - if you can act well, maybe this will make you stand out. Here are some things you can do to prepare.
Think about things you could change to look right for the role. Outfit's usually the easy choice. Hair. Facial hair for men. Elevating shoes - yes, for both genders. Choice of jewelry. Really get into the character's head, envision who they would be, how they would act. If it's an exaggeration, so be it. Become the exaggeration. Get into the character.
Weigh your odds, but if you don't have anything else happening at the time, be more lenient. Think about things that will definitely keep you from looking right for the audition. Were they asking for someone with long hair, and you have shoulder length hair? That shouldn't really stop anyone from trying, right? Worst case scenario, you get another "no" and you're one "no" closer to a "yes".
Be open minded, and just do your best, but keep in mind, if you can't sell it to yourself, most likely you won't be able to sell it to others.
Jeff F. This happened to me once for a short I did. They were looking for a "McConaughey" type which I'm FAR from...but they really liked the fresh take I gave the character so I got the part (premiering at the LA film festival this year - check it out!) :-)
Tomasz M. Congrats Jeff, send me a link, I'll be happy to take a look. My email is firstname.lastname@example.org or post it in the comment.