it is dificult to define a 'spiggy mole child'. it can be one of many things.
1. an insult, refering to someone as a 'spiggy mole child' is a way to call them a dirty reclusive kid.
2. a praise. it someone accomplishes something wonderfully sneaky you can use this phrase to praise them.
3. a term of endearment. 'aw my little spiggy mole child.'
it can always be used as a curse for example if you drop something.
Person 1: Dude? Did you just get with my girlfriend?
Person 2: yeah sorry man.
Person 1: YOU SPIGGY MOLE CHILD.
Person 3: You got with Jess? high-five you spiggy mole child!