what am i, chopped liver?

Etymology:

• Although the origin of this phrase is not really clear, there are two theories. The first theory says that liver was not always viewed on the same level as other foods. For example, if a person is cooking a chicken, they’ll oftentimes throwaway the giblets, you know, like the liver or gizzard. Or instead of throwing the giblets away, the person will cook them, not for themselves, but for their pets to eat. Hence, since liver is not as desirable to eat as other foods, the expression might spring from such an idea.
• Another explanation, as Wikipedia explains, is that “chopped liver was traditionally served as a side dish rather than a main course.” So the idea would be that if a person thinks they are being given less attention than someone else, they might feel like they are being treated like a side dish and not the ‘main course.’
• The oldest written occurrence of the phrase appears in a comic strip from the Ames Daily Tribune newspaper, 1971. The comic is called Winthrop and was written by Dick Cavalli. The above example was what the comic strip characters said.