Title and also uses the same clip (taken from the unfinished serial 'Shada') of the Fourth Doctor punting in Cambridge when he gets by abducted by the time scoop (as an injoke about not being able to get Tom Baker to make an appearance).
Near the end, where Jon Pertwee (Third Doctor), calls Patrick Troughton (Second Doctor) "Scarecrow." Pertwee played the title character in "Worzel Gummidge," himself a scarecrow.