Blitzen fish, or Resurrection fish, were a pan-dimensional species native to the Aurora Gloriousia, in the fourth universe. They were able to mimic death whilst using a nearby power source to grow larger.
Whilst on the planet Quinnis, the First Doctor bought his granddaughter Susan a shrivelled up baby Blitzen fish. They both assumed it was dead but, due to its beautiful colours, Susan wanted it. (AUDIO: Quinnis)
One Christmas day, the Eighth Doctor recovered her room and wished to give it to Susan again as a Christmas present. Unbeknownst to the Doctor, the fish had grown up to seven metres and had hibernated in Susan's room. After reshuffling the location of Susan's room, the Blitzen fish was awakened and started breaching the planes of reality within the TARDIS, jumping back and forth in time, killing Fledershrews along the way.
Behind the scenes
- The Blitzen fish is actually based on the lionfish, which bear similar appendages and stripes. The cast were shown pictures of the fish to help them to visualise what they were being attacked by.