[Da der xkcd-Webcomic auf Englisch ist, gibt's die Beschreibung dieses Caches nicht auf Deutsch.]
[Since knowledge of the English language is required to understand the xkcd webcomic, there is no German cache description.]
This mystery cache is a tribute to Randall Munroe, the ingenious creator of the wildly popular webcomic xkcd. On its website, it is described as "a webcomic of romance, sarcasm, math, and language". Updates are provided each Monday, Wednesday and Friday.
By answering the questions of this cache, geocachers new to xkcd will get to know (and hopefully love) its humour and style. Then again, experienced xkcd readers will enjoy browsing through the history of one of their favourite webcomics 
In order to promote this cache, I want to introduce a "take a comic, leave a comic" policy: before you head to the location of the final, please print out one ore more comics you liked together with the logo provided below and leave them in the cache box. In return, take out a comic you find in the container and place it in any other cache anywhere in the world.
In order to calculate the coordinates of the cache location, you need to answer 12 questions. The first 9 questions require the examination of the standard xkcd comics, while the last 3 questions deal with the recently established what-if section where Randall answers hypothetical questions from random guys like you and me with real physics.
Some questions or hints involve the so-called "comic index". This term describes the number displayed in the address bar of the browser (after the slash sign) when viewing the corresponding comic. For instance, the comic titled "Every Major's Terrible" from http://xkcd.com/1052/ has comic index 1052. That's it.
The questions will require you to browse through several comics; the hints can give you an idea which range of comic indices you have to examine.
So now, enjoy the comics (as well as the corresponding mouseover texts)!
EDIT 28/06/2015: due to several muggled boxes, the cache is now in a new place (close to the last location). The new container is now smaller and therefore does not provide the space for larger comics. So I don't ask you to follow the take-a-comic-leave-a-comic policy from above. However, I printed out and put some small, one-frame comics into the box. If you like one of those, I'd be happy if you took them to another cache :-) of course, also the formula changed slightly. If you already solved the riddles, please recalculate the result.
Comic questions:
1) Which comic features the first appearance of Black Hat Guy (the guy who's wearing a black hat)?
Comic index = A.
2) What would be the median lethal dose of toxicity data for a 70kg heavy person?
Answer (in kilograms) = B.
3) What is the highest number of frames of all comics whose index is a Fibonacci number <1000?
Answer = C.
4) Which number does Black Hat Guy have in mind when he sees a group of two mathematicians and three physicists on a street?
Answer = D.
5) If, on a linear scale, sociology has purity 1 and biology has purity 6, how much purity does mathematics have?
Answer (rounded to the nearest natural number) = E.
6) In the Click and Drag comic (comic index 1110), how many stick figures are drawn between the tree on the original view of the comic and the giant jellyfish in the air (following the ground either left or right)?
Answer = F.
7) How many percent of all the tea in China could Donald Trump purchase, according to the money chart (comic index 980)?
Answer (rounded to the nearest natural number) = G.
8) If 11 is "Friendly", what is 4?
Total number of letters of answer = H.
9) Finish the equation: 
what-if questions:
10) What is the peak power output of Yoda (in kW)?
Answer (rounded to the nearest natural number) = J.
11) How high could a professional pitcher (say, Aroldis Chapman) throw a golf ball?
Answer (in stacked giraffes) = K.
12) If you call a random phone number and say “God bless you”, what are the chances that the person who answers just sneezed?
1/Answer = L.
NEW FORMULA: The cache box is located at N 48° XX.XXX, E 16° YY.YYY,
where XX.XXX =(A+C+D+E+F)*B - G - I - E + C (milli-minutes)
and YY.YYY = L - G*H*(J+K) + (D-C)*I*J - H + J - K (milli-minutes).
Since the GPS signal is inaccurate in the area of the cache (at least on my mobile phone), the coordinates of the final were determined via Google Maps. In doubt, trust the calculated position on the (satellite) map (there are some reference points in close vicinity) instead of wandering around following the GPS signal.
Watch out for dog walking muggles! Happy Hunting!
You can check your answers for this puzzle on GeoChecker.com.