David Gallagher and Tabitha Lupien portray Mikey and Julie respectively. Unlike the previous films, it does not feature the voiceover talents of Bruce Willis, Roseanne Barr, Damon Wayans, Joan Rivers, or Mel Brooks as their interior monologues; rather, Danny DeVito and Diane Keaton provide voiceover roles for their newly acquired dogs, Rocks and Daphne, respectively, and it focuses more on their life.

Who played julie on look whos talking now? Okie... think carefully first, then make a decision:
The relevant information to answer the above question is: David Gallagher and Tabitha Lupien portray Mikey and Julie respectively. So, the answer is Tabitha Lupien.