(colloquial) Declares something as ended or out of the question, just as the life of the mouse in the mousetrap is irrevocably over. The rhyme has a reinforcing effect.

the house is on fire / having a great time

to put the middle finger across the index finger, a gesture made when taking a false oath, either clandestinely to symbolically break the oath, or openly in a jocular manner; to cross one's fingers

(idiomatic) to pull the strings

(idiomatic) to remain loyal to someone, to stand by someone [+dative]

(idiomatic) [+dative] to cook someone's goose

(idiomatic) to give somebody hell [+dative]

(idiomatic) to face the music

(idiomatic) [+dative] to bootlick

(idiomatic) to lose one's cool