Which Star Trek actors have played the most different species?
Some groundwork to keep the numbers 'clean':
One - Let's stick to speaking actors, not stunt actors or the people in monster suits.
Two - Purely holographic or hallucinated characters count as whatever species they appear as.
Three - Changelings, Prophets, and characters in disguise all count as their 'base' species, not the one they're appearing as.
Four - Hybrid characters only count for one species - preferably the one they most match phenotypically, so Spock would only count as a Vulcan, and B'Elanna Torres as Klingon.