Yapples - Yellow apple like fruits that are rather uncommon in forests, however yapples are a special because they are an apple imbued with magic of the feywild, having a delightfully sweet fruity flavor that upon consumption brings joy to weary souls and is known to sometimes cure depression. However even with their benefits one should not consume to many of them for they sometimes can unfortunately cause cackle fever (roll a D100 upon consumption if the user rolls a 3 or lower they are inflicted with cackle fever) They are found growing on trees were the material plane overlaps with the feywild. 

See Cackle Fever in DM’s Guide (Pg: 257)