rrrRobbo, from last to first.
All of the initial letters of across answers (except 39) spell 2 characters from this old fable. One character has two 'I's (if you use a preceding title to his name), and the other character has one 'I'. The same apparent confusion occurs with across answers starting 'N' and 'R'.
Only the first letter moves in the across entries relating to the second character.
27 is an entry where the first letter moves. It ends up starting with 'A'. 6 is a US version of tram tracks.