Isekai Quartet

is a Japanese anime series that serves as a chibi-style crossover between Kadokawa's isekai-genre light novels. There are currently two seasons, with a third confirmed.

Plot
One day, a magic button suddenly appears. The protagonists from KonoSuba, Overlord, Re:Zero − Starting Life in Another World, and Saga of Tanya the Evil all press the button occasionally, unintentionally and move to a parallel world — another brand new Isekai — where a new story featuring high school life begins. With no way of escaping, the characters must lead a normal school life and make acquaintances with the others. One thing is certain: the classroom full of fan-favorite eccentric personalities never gets boring!

Season Two sees them being joined by protagonists from The Rising of the Shield Hero, with the protagonists from The Hero is Overpowered but Overly Cautious making a small appearance.

Official

 * Official Site (JP)
 * Crunchyroll
 * Funimation
 * Twitter (@isekai_quartet)

Other Wikis

 * w:c:KonoSuba
 * w:c:Overlord
 * w:c:ReZero
 * w:c:Youjo-Senki