bàn​lù​shā​chū​gè​chéng​yǎo​jīn

to have a wrench thrown in the works

半路杀出个程咬金 半路殺出個程咬金 bàn​lù​shā​chū​gè​chéng​yǎo​jīn
to have a wrench thrown in the works
literally "Cheng Yaojin ambushes the enemy mid-way"; used to describe someone showing up unexpectedly and disrupting a plan or causing a situation to go wrong

Cross-References

See