This always confuses me. I don't know a lot about how godparenting customs work, but it seems odd that an Orthodox Christian can have Protestant and Catholic godparents. Are all denominations so inclusive?
It varies from church to church. The Church of Norway only says that members of other churches (and other Christians not being member of a church) can be sponsors as long as they accept children baptism.
In Norwegian: https://kirken.no/globalassets/kirken.no/om-troen/gudstjeneste---liturgi/gudst2011_2012_alm_bestemmelser_daap_bokm.pdf (Barnedåp, point 5).
DTH
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