Yes, cherries and plums are both in the 'prunus' genus, so some varieties can be grafted onto each other. It's possible to have a "fruit salad" tree that grows peaches, plums, cherries, and apricots all on one tree.
Generally, though, this is more of a novelty than anything useful. You won't get as much fruit from such a combination, and each variety might have different seasonal timing, so maintenance can be complicated.