The one where Jamie dances the Highland Fling...
The first five or so minutes of this episode consist of a pretty laboured catch-and-escape scenario, with the Doctor and Polly running away from Ola's guards, and Jamie dodging the Macra's giant claws. It struck me only now, four episodes in, that the Macra don't make any sound (except for their control voice). They're huge monsters, this is Doctor Who, so why don't they roar or growl or gnash their fangs (that's if they have fangs - there's certainly plenty of teeth on display on the sleeve of the BBC soundtrack CD!). They must be the quietest monsters Doctor Who ever had (aside from the Weeping Angels).
Everything picks up when Jamie escapes into the main hall where a group of colonists are rehearsing. There's no doubt about it, the chant they're rehearsing is sheer bonkers, and the main cheerleader is as ardent as an American Christian TV evangelist (surely his refrain to recite the chant again "but this time with more feeling" is a sly reference to the 1958 play/ 1960 film Once More, with Feeling?).