In the first season of Prison Break, Michael and others escape from Fox River Penitentiary.
Michael seemed to have planned each and every step thoroughly. In fact, he went into so much detail as to learn chemistry and get an obfuscated tattoo of the blueprints of the prison. He traps Sara in his love (which turned out to be real) to get the infirmary door open.
But when it came to breaking the window bars, he had to improvise at the last moment. Why didn't he plan anything about breaking the window bars?