The one where Leela's eyes change colour...
"Shameleon factor"? What's all that about, Doctor? It's surprising that someone as well-read and knowledgeable as Tom Baker could get the pronunciation of such a word so wrong, but then this isn't a unique example. He also wavers on the pronunciation of Rutan in this episode, while other Doctors have slipped up too, including the Seventh bodging Spiridon in Remembrance of the Daleks, and the Eleventh fudging Metebelis III in Hide.
Within moments of this episode opening, poor, sweet, innocent Vince is killed by Reuben the Rutan, which is such a crying shame. This era is scattered with deaths like these, characters that you get attached to, and so you feel it more when they die (Dr Carter in The Hand of Fear, Runcible in The Deadly Assassin, Casey in The Talons of Weng-Chiang...).