A reader commented that she thought “snuck” was the past tense of “sneak.”
It can be, in a casual sense: Robert snuck into his bedroom to make sure his favorite magazine was well hidden under the mattress.
But in a more formal context, you would write and say, Robert sneaked into the boardroom to retrieve the laptop he had forgotten after the meeting.
Present tense: sneak (snuck is not used in the present tense)
Past tense of either verb: sneaked or snuck
Past participle: has, have or had snuck or has, have or had sneaked.