Some characters are visual puns: 尜 (小大小), 尖 (小大); others are a phrase written as a single character: 膥 (未成肉), 籴 (入米), 汆 (入水), 奀 (不大).
What are some other characters which fit into these categories?
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These are called ideogrammatic compounds. I remember my teacher said about 10% of Chinese characters are ideogrammic compounds, which means there are more than 5,000 of them.
This Wiktionary page lists 270 of them.
This lesson took from an elementary school book analyzes about 10 characters whose original forms were ideogrammic compounds.
You can find some other information on Baidu Baike .