It looks like a runner bean, only smaller.
From the makers of Mangeone...
Mangeone
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Explanation
Experiment
Explain Bear
Listen up, buttercup. The joke is that "Mangeone" sounds like "Mangetout," which is a type of pea that you can eat whole. But "Mangeone" implies you should eat only one. I bet you were planning on eating more, weren't you?