Suppose you have this kind of code

Entry1            LD    C,#10
            JR    MAIN
Entry2            LD    C,#20
Main        some code
            RET

You can save a byte by storing the the second entry in a not used register
pair, like this
Entry1            LD    C,#10
            DEFB  #21
Entry2            LD    C,#20
Main        some code
            RET

The program from Entry1 would look like this
Entry1            LD    C,#10
            LD    HL,#200E
Main        some code
            RET

You save a byte and it is faster
If you need HL you can use another spare register or use a jump condition
that is never true.

Entry1            LD    C,#10
            DEFB  #DA
Entry2            LD    C,#20
Main        some code
            RET

Entry1            LD    C,#10
            JP    C,#200E     ; make sure C is always 0
Main        some code
            RET


Greetings,
Johan Koelman