snuck in

• sneakedMoved to avoid detection
• creptMoved slowly, furtively
• slippedLost traction momentarily
• tiptoedWalked on foot-ends quietly
• infiltratedEntered covertly, secretly

stealthy · shadows · quiet · hidden · backdoor · unnoticed · secret · smuggled · covert · whispered · lurking · prowled · sidled · eased · ninja · intruder · uninvited · gatecrasher