Every GM has their own way of accepting character sheets. With the exception of audition-based methods, I hate hate haaaate it when people who are applying to a roleplay DON'T READ THE CHARACTER SHEETS OF THE CHARACTERS THAT ARE ALREADY A PART OF IT and then proceed to make characters that are VERY similar to one that's already been made.
Character diversity is important to me. And while I think it's totally fine to have a few similarities between characters, it really bugs me when there's like 5 lolis and 5 tsunderes that all have the same backstory/personality/likes/dislikes/magical powers/etc.
I'm pretty sure these people aren't doing this intentionally, but I just don't know why you wouldn't consider the other characters and what they're like before going ahead with your own. Or maybe they are doing that and thinking "to hell with it-- I'll do what I want". I can't say I haven't been guilty of making a character that was really similar to another in the same RP, but that's only when I'm like 90% done with a CS and somebody else posts theirs before me. And even then, I go in and tweak my CS to make sure I'm properly differentiating my character from theirs.
While on the topic of not reading character sheets, there's a special place in hell for people that don't EVER read the CSs of their fellow ACTIVE roleplayers. I spend more time on my sheets then I do on 4 or 5 big posts combined. And I ALWAYS read and make an effort to get to know the other characters. I thought this was like common courtesy or something? Are there a lot of people out there doing this? Why??
