> eg a relative jump that jumps into the middle of a multibyte instuction
> that uses PART of that instruction as a different instruction. I have
> seen that done (code was probably written in assembler)

It's quite common to use this technique in 65xx code with the non-
destructive BIT test instruction, for example when loading the
accumulator for tables or strings etc

BIT = 2C, LDA = A9

BIT $00A9   2C A9 00
BIT $01A9   2C A9 01
BIT $02A9   2C A9 02

etc

Using a computed GOTO or branch it's easy to jump to an A9 and so
perform an LDA, (which is then followed by irrelevant BIT instructions,
then you hit the exit to the function routine), eg

LDA #01
BIT $02A9
JMP xxxxx      ; JUMP to xxxx with 01 in A

I don't believe this is possible with PICs though

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