As stated above if you have a full 4 years left, join as a fish. You learn so much about yourself and build so much character that year that it is a huge deal.
We had two frogs that joined in my pisshead year and I must say they were a bit out of place for that entire year. The fish aren't allowed to have much interaction with them and don't know how to react to them and resent them for sure, the upperclassmen are pretty tough on them and as a buddy you somewhat resent them because they didn't get the full fish experience that the rest of your buddies went through with you.
That being said, by our Junior year, one was one of the gang, and the other... well he joined staff and was never really part of the class.
We had a guy attempt to frog in for the class two below me and couldn't hack it. Problem was he didn't fit in and was never going to, so he went to the Trigon and made a bunch of accusations about hazing and got a lot of us kicked out completely from the University and almost had criminal charges pressed. Some were finally allowed to re-enter the University after a year, but the damage done was life changing to say the least and was far more hard to deal with.
We also had the rare alligator that showed up as a Junior in the class above mine and that just flat out didn't work.
If you have to frog in, work your ass off and earn it like you are trying to make up for it. Your buddies will respect you more and so will the underclassmen.
Whatever you do, if you decide to punch, don't be a baby about it and just move along. It is a lot tougher road psychologically to frog in.
Firearms and LTC Instructor
12thGun.com
Jarhead
CO of P-2 Class of ‘96