Dragon Ball Z - episode 17 - 29 Aug, 1989

Mr. Popo leads Earth's top warriors to Kami's Pendulum Room where the past, present and future exist at the same time. After an eventful trip back in time they all realize they have to train a lot harder if they are going to stand a chance against the two Saiyans who are speeding ever closer to Earth. (Source: dbzepisode.org)