The German noun der Bock means a mammal of the male gender, similar to the English word "buck," and is often particularly used to describe a male goat or "billy goat." However, the expression Bock haben auf or keinen Bock haben auf has a meaning quite different from what you might expect based on the direct translation of the noun!

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Blumio hat Bock auf gute Unterhaltung.

Blumio is keen on good entertainment.

Caption 6, Blumio - Rappen für gute Unterhaltung

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Oh, zerkleinern, das macht mir Spaß. Da habe ich Bock drauf.

Oh, chopping, that's fun. I'm up for that.

Caption 10, CHoE Rocker - Profi-Grilltipps

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Sie hat Bock auf Shopping, also in die Stadt

She feels like shopping, so it's off to the city

Caption 23, Cro - Bye Bye

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Ey, Nina, hast du Bock auf 'ne Wurst?

Hey, Nina, do you want to go out for a wurst?

Caption 6, Die Pfefferkörner - Cybermobbing

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The slang expression Bock haben auf is the equivalent of the expression Lust haben auf and may be translated in a variety of ways. Note that if a noun follows the preposition auf, then the noun case should be accusative. When you use the expression as a negation, just place the accusative case of kein in front of the masculine noun Bock: 

Jeder kann so seiner Wege gehen,

Everyone can go their own way

wenn er keinen Bock auf die anderen hat.

whenever they aren't in the mood to be around the others.

Caption 47, rheinmain - Szene Selig

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Jedes Mal, wenn du von deiner Arbeit,

Every time when you come home from your work,

von deinen Führungen, nach Hause kommst, bist du fertig,

from your tours, you are exhausted,

hast keinen Bock mehr auf irgendwas.

don't want to do anything.

Captions 28-29, 12 heißt: Ich liebe dich - Kapitel 4: Liebe auf den ersten Blick

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You may also use the phrase in the form of question, in which case auf becomes worauf:

Worauf hast 'n du Bock?

What are you up for?

Caption 29, Mario Barth und Paul Panzer - Männersache

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Further Learning
Read the Duden dictionary page for der Bock and scroll down to Wendungen, Redensarten, Sprichwörter to read other expressions related to this noun. You can also go to Yabla German and search for other examples using the noun der Bock to see other contexts where the phrase is used.

While the appreciative audience for bad puns on Oscar Wilde play titles may be limited, it is important to know if somebody is being serious or not in German, especially when your goal is to achieve a proficient level of communication in that language.

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If Johanna and Julia both have husbands named Ernst, and somebody announces to them that a man named Ernst is on the telephone, Johanna might ask Julia Das ist nicht dein Ernst, oder? to see if Julia's husband is calling or if it's her own husband on the telephone. In all other cases, however, a reference to the noun der Ernst ("seriousness") preceded by a possessive pronoun (mein, dein, Ihr, euer, unser) means something else altogether: 

Das is'... das ist nicht dein Ernst, oder?

That is... you're not serious, right?

Caption 24, 12 heißt: Ich liebe dich - Kapitel 4: Liebe auf den ersten Blick

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The phrase would translate literally (and rather clumsily) as "Is that not your seriousness?," but what is meant is "You're not serious?"

Here's another example of the phrase, this time with the second person plural possessive pronoun: 

Des isch net euern Ernscht [Dialekt, das ist nicht euer Ernst]!

You can't be serious!

Caption 71, Die Pierre-M.-Krause-Show - Classics

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Another way of stating whether somebody is being serious or not is to use the noun der Ernst preceded by the dative preposition in: 

Das meinst du nicht im Ernst.

You can't be serious.

Caption 17, Mama arbeitet wieder - Kapitel 2: Kompromisse zu finden ist nicht einfach

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Im Ernst is in fact the most common way to say "seriously": 

Nein! -Ja, ganz im Ernst.

No! -Yes, seriously.

Caption 11, Barbara Schöneberger - Bambi-Verleihung backstage

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Further Learning
If you are taking your German lessons seriously, you can go to Yabla German and find other uses of der Ernst in a real-world context — excepting, of course, the rare occasion when Johanna or Julia's husband Ernst shows up!