Alternatives to "no mames"

No mames is a very infromal and solid expression of desbelief or repudiation. Most people circumvent the informality by using alternative expressions that, preserving the intended meaning, show the speaker's regard for formality. Those expressions hint to what the speaker would like to say by sharing only the first syllables of no mames and the like. The literal meaning of the interjection is irrelevant but usually very colorful. Here are some popular examples:

You sort of say: ¿No va a venir tu mamá? [lit. isn't your mom coming?]
You actually say: No mame...¿nir tu mamá?

You sort of say: No me amenaces [lit. do not threaten me]
You actually say: No mame...naces

You sort of say: No mouse, Mickey
You actually say: No maaaaa...us Mickey

You say: No maaa...nches tu alma [lit. do not stain your soul]

You sort of say: No se llama mona, se llama muñeca [lit. it is not called figure, it's called doll]
You actually say: No sea mamón a... se llama muñeca

Vale verga, valeverga

The expression valer verga literally means "to be worth a penis." It is used to denote worthlessness. However, when used as an interjection in reference to a situation, ¡vale verga! or ¡ya valió verga!, means that something went terribly wrong and that there is no way to make it right. Finally, the term valeverga is used in reference to someone who does not care about what other people say, the law and social norms, his or her own future, politics, etc. A valeverga or valeverguista is someone whose answer to most questions would be me vale verga (lit. it's worth a dick to me.)

Paco: Ya valió verga el pase a cuartos de final.
Pepe: Mmmm... me vale verga.
Paco: No cabe duda de que eres un verdadero valeverguista.

Paco: We're done. We didn't make it to quarter finals.
Pepe: Hmmm... I do not give a damn.
Paco: You are a truly devil-may-care mofo.

Catafixiar

Catafixiar (cat-affix-EEAR) is a verb that means to barter in an abusive and frustrating way. It comes from the TV show "En Familia" hosted for over 40 years by Javier Lopez "Chabelo". At the end of each episode, when game participants have already collected their prizes, Chabelo offers them a barter in which they give up their prizes and get an unknown gift, in one of three catafixias. One of the three catafixias has a bogus gift (e.g. a big glass container for aguas frescas). Another has cheap furniture. The third catafixia contains toys and it is the one everybody considers worth the risk. Unfortunately, the chances of getting the good prize are 1/3, so in average playing the catafixia is a losing strategy.

Alma Verónica: Pensé que me ibas a llevar a un restaurante de lujo.

Juan Alberto: ¿Qué te parece si te lo catafixio por una tortas para llevar y una visita relámpago al cinco letras?

Alma Verónica: I though you were going to take me to a fancy restaurant.
Juan Alberto: How about picking up some subs and stopping by a motel instead?

Democrático

The term democrático (lit. democratic) has come to mean for the people. Since Mexico is a country with a small middle class and a gigantic mass of poor people, democrático is interpreted as for the poor. In every day speak, democrático is used as a reference to public trasportation. Democrático is a short version of democrático pesero (microbus) or democrático metro (subway).

Diego: Dejaste tu nave con el valet?

Gael: Nel, me vine en democrático.

Diego: Did you valet park your car?
Gael: Nope, I took public transportation.

Firma versus Poderosa

In Chilango slang, firmar (feer-MAR, lit. to sign) or echar la firma (eh-CHAR lah FEER-mah, lit. to throw the signature) means to urinate. By splashing urine one leaves a distinctive mark, similar to, but more primal than, a John Hancock. If you are in Mexico City and you actually mean to sign, the appropriate term is echar la poderosa (poh-the-ROSS-ah, lit. to throw the mighty one). One's poderosa is one's signature.

Ejecutivo de cuenta: Sr. Menganito, nada más nos falta su poderosa, y el efectivo le será entregado en la caja 3.
Sr. Menganito: En cuanto termine de echar la firma, si me permites.

Account manager: Mr. Menganito, we only need your signature and you'll get the cash at teller number 3.
Mr. Menganito: As soon as I am done here, if you don't mind.