Doraemon (1979)

The Snail House Sure is Carefree (1x87)

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Nobita gets called a liar by his mom when she believes him to be hiding his recent exam. Nobita complains to Doraemon and exchanges his snacks for a snail shell that protects him from his surroundings. Shizuka shows up near the end and returns a journal that holds his exam grade. Nobita's mom apologizes, but is met with Nobita's demands... until she asks him for his grade.