Bring In a Ringer
Tip #16 for shattering writer's block
Introduce a completely new character or voice in your work. Write them in, out of the blue, with no backstory, and let them start talking. Have them react to the circumstance, comment on your established characters, say the thing nobody else will say. Shake things up with some new blood.
This tip is from 19 Tricks to Shatter Writer’s Block. If you missed any of the previous tips, you can find them all in the Hack Your Noodle section of Read Write Repeat.