Doctor Who: 8 Reasons Donna Noble Saved The Doctor
6. Supertemp (The Sontaran Strategem/The Poison Sky)
There are several moments in this great two-part episode that show what an asset Donna has quickly become to the Doctor in their short time together. After receiving a call from previous companion Martha Jones to come back to Earth, she and Donna quickly befriend each other - to The Doctor's chagrin!
The Doctor and Donna then set about exploring the ATMOS plant, the very reason that Martha summoned him. While The Doctor tries to figure out what exactly is happening, it is Donna who discovers the biggest clue of all - using her office temp knowledge. She simply goes to the H.R. department and discovers that no one has ever taken a sick day in the plant - tipping The Doctor off that the people working there are clones, further leading him to figure out that the entire plan was devised by the Sontarans.
Not bad for a temp from Chiswick really! This episode also saw the re-introduction of the Noble family, which would later serve to help The Doctor as well!