Usage note on Snuck:
First recorded in writing near the end of the 19th century in the U.S., snuck has become in recent decades a standard variant past tense and past participle: Bored by the lecture, we snuck out the side door. snuck occurs frequently in fiction, in journalism, and on radio and television, whereas sneaked is more likely in highly formal or belletristic writing. snuck is the only spoken past tense and past participle for many younger and middle-aged persons of all educational levels in the U.S. and Canada. It has occasionally been considered nonstandard but is so widely used by professional writers and educated speakers that it can no longer be so regarded.
Usage note on irregular verbs:
American English normally uses the regular form, while British English tends to favor the irregular. In other cases, such as dive (dived vs. dove) and sneak (sneaked vs. snuck), the opposite is true. Australian, New Zealand and South African English tend to follow the British practice, while Canadian English often sides with the American usage.
Source: Webster Dictionary