When Karl says "I'm a doctor, not a blood bag" it is a reference to a reoccurring line in Star Trek.
Not only does the android doctor say "I'm a doctor, not a blood bag!" with the classic Bones/EMH/Julian Bashir delivery, but with Red Dwarf's resident android Kryten's face.
The android doctor presents himself as "Karl", maybe another nod towards Star Trek? The reboot of Star Trek featured actor Karl Urban as the doctor of the original series USS Enterprise, dr McCoy.
Niamh Algar and Cosmo Jarvis both appeared in Calm With Horses.