Hey Juca... This is how i'd "slan'l8" ur dialogs lol
Guy 1: Hey Robert, u hvnt been studyin' English to much, dat way u'll blow da test!
Guy 2: Get off it! I no all da lesson - I dont need to study.
Guy 1: U gotta hit da books if u wanna pass a grade!
Guy 2: I got it man. I'm inna eighth grade - I no how it goez down.
Guy 1: Oops! Sorry.. Didnt mean to hit upon u..
Guy 2: Chill out dude, it's kewl.
As donay said before, there r countless possibilities in the slang field and yeah, their supposed to change from place to place and even inside the same country there'd be variations e.g there r slangs in Philly that ppl in LA r unaware of or simply dont use and vice versa. Anywayz, I hope I could help...
PS. U said Homer said "lay off" and it was turned as "se liga"... That's just one more of the several possibilities. U could also say, "get up off my nuts" (qndo alguém está enchendo seu saco como é o caso do cara 1 falando pro cara 2 q ele precisa estudar pra ir bem na prova).