People say crackships within a series for characters that never interacted. Ex: People think Eridan x Roxy is a crackship since they never met. The kernelsprite self doesn't count either. Another example of a crack ship would be something like Dualscar x Mom Lalonde. Ships that is from other franchises is crossover ships. Mine being Eridan x Azul Ashengrotto from Twisted Wonderland as avatar related.