BERLIN — In what turned out to be the weakest weekend at the German box office this year, “What Happens in Vegas” surprised local exhibs by topping the charts, while “Speed Racer” crashed and burned on its first lap.

Sunny weather kept Teutons outdoors and cinemas nearly empty over the three-day Pentecost holiday weekend, resulting in a 49.4% overall drop at the box office.

Only 175,000 people nationwide bothered to go see the Cameron Diaz and Ashton Kutcher romantic laffer, giving it a $1.8 million take from 500 locations.

Warner Bros.’ “Speed Racer,” which has received plenty of press here due to the fact that it was entirely shot at Studio Babelsberg outside Berlin and was partially financed by federal and regional film grants, has become one of the biggest flops ever at the German box office.

Opening at number nine at 590 locations, the Wachowski pic attracted a total of 14,443 viewers, managing to scrape by with only $146,908 — a per-location average of only $250.

One exhib attributed the pic’s failure to not only negative reviews and a lack of familiarity among Germans with the 1960s toon series upon which it’s based, but also to a possible aversion to its brightly colored and hyperkinetic graphics.

“I think people saw this computer game world and were not impressed. It was not something they wanted to immerse themselves in for two hours.”

In its second frame, “Iron Man” plunged 68% to $1.1 million, landing it at number two, while local teen drama “Sommer” came in third with just $348,346 in its fourth frame for a $5.3 million total.

The only other new entry into the top 10 was 3L’s Spanish horror film [REC], which opened ahead of “Speed Racer” in eighth with $161,391 from 105.