You cast a spell that causes the spirit of the targets mother to appear for one minute, during that minute the spirit berates the character or monster continuously about their work ethic, life choices, cleanliness, why they aren't married or in a long-term relationship, the mothers lack of grandchildren, and other misc. motherly concerns.

Possibly annoying. The spell always has a chance of being cast on the castor. Roll a D100 to see who is effected. Everyone within 50 feet radius of caster is a potential target, including caster. Dungeon Master specifies numbers. 

Example: You cast "Your Mom". If there are 5 people within range of the spell (Including caster), there is a 20% chance spell will target the caster, The caster always takes the lowest percentage ie. 1-20 in this example, target 2: 21-40, target 3: 41-60, and so on.