well freak the mighty is where two outcasts, one small crippled extremely smart kid, and a big strong confused kid get together after being neighbors. The theme of freak the mighty is most likely friendship and dont judge a book by its cover because altough they were verydifferent boys, they still got to be best friends. (SPOILER AHEAD JUST GO TO THE BOTTOM IF YOU DONT WANT IT) It could also mean to appreciate your time with whoever you are with, because since freak dies, the other kid is very sad about it.
Appreciate your time with whoever are you with, but since this is least likely go with the other two.