This is no April Fools joke, Google is really showing the same search result for some queries in special cases. A WebmasterWorld brought it my to attention and then I was given a way to reproduce it by Andreas.
The first thing you need to do is limit your search results to show only one result per page. You can do that by adding &num=1 to the URL string after searching. Even after I tried that, for a search on ipod, I was unable to reproduce the issues on the results 57 and 58 as an example.
So Andreas emailed me an example that works. A search on "deine Tierwelt" in Google.de returns this result for position number 57:
And the same result for 56:
What seems interesting is that the "results of X" line at the top right keeps changing as you change results. Seems like a weird bug that I cannot reproduce in Google.com.
Forum discussion at WebmasterWorld.