Picking a person who has done movies in the same genre doesnt mean they play the same character.
Im sorry, but Ben Stiller's character in Dodgeball is nothing like the character he plays in Zoolander. Reality Bites, There's Something About Mary, The Royal Tenenbaums, Tropic Thunder, Greenberg...different characters.
Will Farrell, he is a comedian, it doesnt make his characters all the same. Buddy the Elf is very different from Mugatu and Frank the Tank. He does have characters that are similar, like Ricky Bobby and Chazz Michael Michaels, but that doesnt mean he doesnt have different characters like Harold from stranger than fiction.