半路杀出个程咬金

bàn lù shā chū gè chéng yǎo jīn

lit. Cheng Yaojin ambushes the enemy (saying)

fig. sb shows up unexpectedly and disrupts the plan; sb whose presence is regarded as irksome

bàn

half

road (CL:條|条[tiao2])

shā

to kill; to slay; to murder; to attack

chū

variant of 出[chu1] (classifier for plays or chapters of classical novels)

variant of 個|个[ge4]

chéng

rule

yǎo

variant of 咬[yao3]

jīn

gold