The Apostle Paul, on more than one occasion, compared the followers of Jesus to a human body...even to the point of calling the church, "the body of Christ" (I Corinthians 12:27).
In the twelfth chapter of First Corinthians, Paul emphasizes that no member of the body is more important than another, that our differences are necessary, and that we all belong together: You can easily enough see how this kind of thing works by looking no further than your own body. Your body has many parts - limbs, organs, cells - but no matter how many parts you can name, you're still one body. It's exactly the same with Christ....I want you to think about how all this makes you more significant, not less. A body isn't just a single part blown up into something huge. It's all the different-but-similar parts arranged and functioning together. If Foot said, "I'm not elegant like Hand, embellished with rings; I guess I don't belong to this body," would that make it so? If Ear said, "I'm not beautiful like Eye, limpid and expressive; I don't deserve a place on the head," would you want to remove it from the body? If the body was all eye, how could it hear? If all ear, how could it smell? As it is, we see that God has carefully placed each part of the body right where he wanted it. (I Cor. 12:12-18 MSG)
I like that one phrase: It's all the different-but-similar parts arranged and functioning together.
In his letter to the Christians in Ephesus, Paul repeats the idea that each part of the church/the body has an important role to play: From [Christ] the whole body, joined and held together by every supporting ligament, grows and builds itself up in love, as each part does its work. (Eph. 4:16 NIV)
To put the analogy in practical terms, if you're a person who speaks words of encouragement or teaching, you might be thought of as being the mouth of the body. If you are always helping others, you could be compared to the hands. Maybe you offer transportation to doctor appointments, etc. for the elderly, or drive people to the church services...just like legs.
If your sole contribution to the life of your church is coming into a particular building on Sundays and sitting...there's a different part of the body to which you might be compared.
Truth is...every body needs a butt, but each body only needs one.