John Lydon (the former Johnny Rotten) was originally approached for the role of Jimmy and even screen-tested for the role. However the distributors refused to insure him for the part and he was replaced.
The scene in the pie shop where Jimmy goes for a bite of "pie, mash and liquor" was shot inside A. Cooke's Pie & mash shop in Shepherd's Bush, London, 48 Goldhawk Road. The Who began their career in Shepherd's Bush, performing their early gigs at the Goldhawk Social Club (205 Goldhawk Rd).
On the front of the scooter that Jimmy steals from Ace are the yellow initials "GS". These initials do not actually stand for Gordon Sumner, the real name of Sting, who plays the part of Ace Face. 'GS' stands for Grand Sport, a popular model of Vespa scooter in the 1960s.