The common expression buscarle tres pies al gato applies to a person who is irritating someone, who may be losing his or her patience, by being very argumentative, and trying to prove something that cannot be proved with arguments that serve no purpose. People who love arguing or who have an impulse to always being right, have a tendency to split hairs. This expression is applied to those who try to prove the impossible with sophisms and fallacious arguments. Buscarle tres pies al gato is to complicate matters, to make Ilife difficult and also to ask for trouble looking for far-fetched approaches to simple situations.
To split hairs
Buscarle (los) tres pies al gato
To not say a word
Sin decir ni pío
To bite your tongue
Morderse la lengua
To get down to business
Manos a la obra
Six in one, half a dozen in the other
De lunes a martes
You scratch my back and I'll scratch yours
¡Hoy por ti, mañana por mí!
If you want to make peace, prepare for war
Si las barbas de tu vecino ves cortar, pon las tuyas a remojar
To speak ill of someone/To get jealous
¡Poner verde!
To fight like cats and dogs
Llevarse como el perro y el gato
To backfire
Salir el tiro por la culata - Salir rana
Don't pee on my leg and tell me it's raining
A otro perro con ese hueso
To fit like a glove
Venir como anillo al dedo
What's done is done
A lo hecho, pecho
Period, moving right along
Punto pelota / a otra cosa, mariposa
To have a blowout
Ponerse las botas
To bite the bullet
Hacer de tripas corazón
To make someone jealous
Poner los dientes largos
To let bygones be gybones
Hacer borrón y cuenta nueva
To have connections
Ser o estar enchufado