‘Snuck’ is sometimes used as the past tense of the verb ‘to sneak’. But ‘sneak’ is regular, which means the past tense is ‘sneaked’.
So where has ‘snuck’ sneaked in from?
I believe it was originally used in a humorous way by people who were well aware of what they were doing. A cartoon cat might use it – Sylvester, for example – while a bishop would not.
Another example of this process occurs in the phrase ‘Who’d have thunk it?’ Everyone knows the past tense is actually ‘thought’.
But ‘snuck’ has been used so often that some people are now accepting it as the correct past tense of ‘sneak’. I came cross ‘snuck’ very recently in the Stockholm Octavo by Karen Engelmann and it was not used in humorous way.
So it may be that humorists, like everyone else, can alter the course of language.