A joke you have to explain cannot be very funny, nevertheless, some hints may be usefull, explaining certain private allusions, or allusions that could be hard to understand for the non-german reader.
To start with, Ôtomo-no Tabito is a real japanese person; he died in 731 and was famous for his poems. He never searched a red flower, and he didn't live in the time of the reign of emperor Go-Tabo, who in fact lived from 1180 to 1239 (and edited the famous Shinkokinwakashû).
The famous critic shows the face of Marcel Reich-Ranicki; the tale of the nazi-aliens is based on some legendary distortion of history in Germany, were the nazis are often regarded as something like aliens from outer space, coming from out of the void, and having nothing to do with the germans.
You certainly know who Bertrand Russell was; Luise Rinser is a german writer, and maybe the worst writer in the world.
When I read about the marriage of Pamela and Tommy Lee, I thought: just how a working class marriage is sometimes imagined.
The phone boxes in Germany used to be yellow in the past, like anything else that had to do with post or telephones. After the semi-privatisation of the german telecommunication company, they decided they need a new corporite identity and started to paint evreything white, grey and pink, with the result that telephone boxes are harder to spot.
The first two quotes of the strange-zone are obvious; the third one is taken from James Joyce's Finnegans Wake.
Peter Hintze is the speaker and prime propagandist of the CDU, the leading party of germany. He started as a vicar, and is famous for his ability of distorting the truth. Leon Henkin was a logicist inventing the Henkin.sentences, some kind of counterpart of the Gödel-sentences. A Henkin-sentence states to be true, like this: "This sentence is true". It is not easy, but possible to show that a variation of the Henkin-sentence is true.
Kafka recites some travestated quote of his doorkeeper-parabel.
The woman interviewed about her opinion about showing Lenas underwear shows the face of Alice Schwartzer, a famous feminist in Germany.
The excurse about the sexuality of mushrooms is absolutly correct, to my best knowledge.
The fish was a secret symbol for the early christs (as fish=IXTOS=Iesus Xristus World's Salvator), and adopted by some old fashioned strict protestantic sects.
The words that call back the fish is a quote from a german tale, collected by the Grimms, ,,Der Fischer und sine Fru''
To be continued.