Hi Gevson,
Creating these sort of voices requires a bit of audio knowledge and lots of trial and error. For Pennywise, I've done some testing myself and you can try a combinations of effects similar to this:
1. Add a reverb which add like a smooth reflection in a room type of effect to the sound. Try diffusion values 20% to 50% and see how it sounds.
2. Add a high pass filter and try frequencies 200 - 700 or so. This should make it sound more creepy, mechanic type of voice.
3. Add an either pitch shifter or voice pitch shifter. Play with pitch value to either get a more thinner or thicker voice depending on how you like the end result best.
Hopefully this should give you some idea on how to create a voice effect like a pennywise.
Cheers,
Yusuf