1. Sister missionaries are frumpzillas.
Sister missionaries have ample space to express their personal style. Our mission president's wife told us to wear COLOR. Now, for those of you that have received that lovely mission prep pamphlet that came with your mission call, pictures would prove otherwise. But we're keeping up with the times. And rumor has it that they are even recreating that pamphlet that they send. Or it's already in circulation. I'm not sure. I haven't seen it, but I've heard about it and heard others talking about it.
2. Sister missionaries are on their mission because they had "nothing better to do".
I had plenty of companions that were at a stable point in their life. Working, going to school, about to graduate, etc.
3. Sister missionaries are on missions because they couldn't get married.
Now, although I wasn't dating anybody before I left on my mission, it doesn't mean that other sisters weren't. I have known several sisters that were in perfectly happy, healthy, functioning relationships before they left on their mission.
I would say that those are the top three. If you've heard any others, send em my way. And I'll be more than happy to bust them.