An Earth Day musical on Nickelodeon; HBO’s moving story of ‘Benny’ Discovery does dinosaurs

In the HBO reality-based special Someone Had to Be Benny (Sunday at 7 p.m.), a 15-year-old suffering from a fatal liver ailment is determined to choose how his disease will be treated and how he will spend his remaining months of life. Benny must fight his doctors and the courts to get his choice. For the entire family.

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A version of Rudyard Kipling’s classic Captains Courageous, published in 1897, arrives on the Family Channel (Sunday at 7 p.m.). The adventure tells the story of a spoiled 14-year-old millionaire (Kenny Vadas) who falls off a cruise ship and has his life changed by fishermen who rescue him. For ages 10 and up.

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In Zanzibar, Rocko and his friends celebrate Earth Day with an environmentally themed musical (Nickelodeon, Sunday at 7:30 p.m.; repeats Monday at 7:30 p.m.). For the entire family.

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Discovery Channel uses research, computer graphics and animation to give a close-up view of tyrannosaurus rex in the premiere of The Ultimate Guide: T. Rex (Sunday at 9 p.m.). The premiere is part of Discovery’s Dinosaur Week. For the entire family.

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In Beast Wars, a high-tech animated children series premiering this week (KCAL, Monday at 7 a.m., repeats Tuesday at same time), two cybergenetic advanced groups fight for control of the galaxy. For ages 8 and up.

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Born Free: A New Adventure, on ABC’s “Saturday Night at the Movies” (8 p.m.), is an update of the original classic. For ages 10 and up.