 Ron Howard (qv) at first passed on playing Richie in the 1960s,  because he didnt want to "be a teenager the rest of my life" on  television. He reconsidered when Garry Marshall (qv) promised him  that, if the series were picked up, Richie and his friends would  graduate high school and become adults (even Fonzie went back to  night school, to graduate with the gang).