I think the shrimp virus thingy's lungs (or whatever the organelle equivalent is) were probably regretting the whole become-a-giant-and-need-way-more-oxygen plan by like minute 3 seeing as it couldn't even move by itself.

K-9 my beloved welcome to the show!!! The inside of the doctor's mind is visually stunning and the crew did a wonderful job of the sets. Overall the plot of this serial is absolutely bonkers with so many bizarre turns it's engaging all the way through.