Cockney Alphabet

It has to do with pronunciation, not content. There are a number of variations (C for miles/C for yourself, Y for husband/Y for Mistress) but these are the more common.
The Cockney alphabet, also known as the Surrealist alphabet, is a humorous recital of the alphabet, parodying the way the alphabet is taught to small children. The humour comes from forming unexpected words and phrases from the names of the various letters of the alphabet.

A for 'Orses .................. ('ay for 'orses)
B for Mutton .................. (Beef or Mutton)
C for Miles ................... (See for Miles)
D for Ential .................. (Differential)
E for Brick ................... ('eave a Brick)
F for Vescence ................ (Effervescence)
G for Get It .................. (Gee, forget it!)
H for Bless You ............... (Aitsshfa! A Sneeze)
I for The Engine .............. (Ivor the Engine)
J for Oranges ................. (Jaffa Oranges)
K for Restaurant .............. (Cafe or Restaurant)
L for Leather ................. ('ell for Leather)
M for Sis' .................... (Emphasis)
N for Lope .................... (Envelope)
O for The Wings Of A Dove ..... (O! for the Wings of a Dove!)
P for Relief .................. (?!?!)
Q for A Bus ................... (Queue for a Bus)
R for Mo' ..................... ('alf a Mo')
S for Rantzen ................. (Esther Rantzen)
T for Two ..................... (Tea for Two)
U for Me ...................... (You for Me)
V for La France ............... (Vive la France)
W for The Winnings ............ (Double you for the Winnings)
X for Breakfast ............... (Eggs for Breakfast)
Y for Husband ................. (Wife or Husband)
Z for Wind .................... (Zephyr Wind)