Combine cream cheese and shredded chicken. If your cream cheese isn't room temperature, you can heat water in a glass in the microwave, then discard the water and turn the glass upside-down over the cheese. Just a few minutes in that warm glass and the cheese will be well along the way toward being soft enough to stir!
Add shredded cheese and stir to combine. I like to use a mix of pepper jack cheese sometimes for a little kick, but any cheddar or Monterey jack will do.
Add ranch seasoning and diced tomatoes and gently fold in until combined. You don't want the tomatoes to break up, but you do want it fully combined.
Fill taco shells with chicken mixture and top with crumbled bacon and chopped green onions.