Protist’s are organism that belong to animal kingdom and are mostly single celled and in some cases multicellular. These organisms are most diversely classified group of organisms and do not belong to any single kingdom.
Thus the common features (internal and external) that should be used in cases of protists are –
An organism should possess cell (internal feature) and its component (must be a living being) and it can be unicellular or multicellular (external feature)