When trying to describe someone who has snuck in, it's important to have an arsenal of synonymous phrases to choose from. Some alternative ways to say snuck in include slipped in, crept in, slunk in, sidled in, skulked in, tiptoed in, infiltrated, or slipped past unnoticed. Each of these phrases has subtly different connotations: for instance, "infiltrated" or "slipped past" might suggest a more deliberate, intentional act, while "crept in" or "tiptoed in" might imply more stealth. Nonetheless, all of these phrases serve as useful and interesting synonyms for "snuck in" in conversation or writing.