Subject + 混进 + Place/Group
混进 (hùnjìn) means "to sneak into" or "to infiltrate." It describes the act of entering a group or place by deception, blending in without being noticed or without proper qualifications.
他拿着假证件混进了公司大楼。
Tā ná zhe jiǎ zhèngjiàn hùn jìn le gōngsī dàlóu.
He used a fake ID to sneak into the company building.
那只猫不知道怎么混进了教室。
Nà zhī māo bù zhīdào zěnme hùn jìn le jiàoshì.
That cat somehow snuck into the classroom.
几个小孩偷偷混进了电影院。
Jǐ ge xiǎohái tōutōu hùn jìn le diànyǐngyuàn.
A few kids secretly snuck into the movie theater.