7x10 - Dragon Ball Z: Dragon Box

Unable to leave the Room of Spirit and Time, Boo becomes infuriated at the thought of never again being able to eat candy! His shout creates a dimensional opening, and he escapes outside, leaving Gotenks and Piccolo behind. Gotenks, having seen Goku do it earlier, successfully transforms to turn Super Saiyan 3! With the same sort of shout that Boo used, they are able to escape from the Room of Spirit and Time.