The literal cliffhanger in which the Doctor lowers himself over a guard rail to dangle over an abyss from his umbrella for no apparent reason comes under frequent criticism for its seeming absurdity. As scripted, the Doctor did have a logical motivation for his actions. According to Andrew Cartmel in a later interview, the passage leading to the cliff was meant to be a dead end, leaving the Doctor no option but to scale the cliff face. As shot, however, this reasoning became unclear.
The last appearance of Mel and the first appearance of Ace.
Sylvester McCoy ad-libbed the scene where the Doctor goes to pet an alien that then tries to bite him.
The script originally featured the Seventh Doctor's trait of mixing up proverbs. John Nathan-Turner and Andrew Cartmel had decided to tone down some of the more overtly comical aspects of the new Doctor's personality, and so these were removed.
Kane was named after Charles Foster Kane, the protagonist of Citizen Kane (1941). His former accomplice, Krylla, was correspondingly altered to Xana, after Xanadu, the name of Kane's estate.