Fate series creator Type-Moon is known for their elaborate April Fool's jokes. Last year, they set up an idol agency for the characters. There was a "Red" Saber KanColle playthrough and various other goods. This year, there was a malfunction in the Chaldea Gate that saw Type-Moon's site, as well as all the servants in smart phone RPG Fate/Grand Order, scrambled in the style of irreverent manga artist Riyo (author of very real tutorial manga).
If you're note familiar with Riyo's (believe or not official) Learn FGO With Manga strips
Elsewhere, there was a special Osomatsu-san mash-up for April Fool's