Chrisitan Witnesses and Proxies
A Godparent is required by Canon Law to be a fully initiated Catholic in good standing. This means that they have to have received Baptism, Holy Communion, and Confirmation in the Catholic Church, and if they are married, they must have a marriage recognized by the Catholic Church. A non-Catholic then cannot serve as a Godparent in a Catholic Baptism because a Godparent is asked to promise to help the parents of the child to raise the child in the Catholic faith.
However, there can be a non-Catholic Christian that can serve as a Christian Witness to the Baptism, but this is not the same thing as a Godparent and the Christian Witness will not be listed as a Godparent in the official record.
If Godparent(s) cannot be present at the Baptism, a Proxy can be designated to answer the parts of the Godparents during the ceremony itself. They should meet the same qualifications as Godparents (listed above) but do not have to take classes or fill out the Covenant Form. They will be listed on the baptismal record as "proxies."