Ravana, Vibhishana and Kumbhakarna performed severe austerities and appeased Brahma. He granted them boons. Ravana wanted that he should not be killed by non humans. Vibhishana wanted absolute devotion to Lord Vishnu.
Kumbhakarna wanted ' NIRDEVATVAM ' ( ability to vanquish devas ). By slip of tongue he ended up saying ' NIDRAVATVAM ' ( sleepfulness ) which was readily granted. Ravana requested Brahma to take back the boon following which his sleep got reduced to six months in a year.
Indra killed Tvashta's son. Tvashta performed somayaga without inviting Indra who came in and forcefully drank the soma juice. Out of anger, Tvashta poured the remaining soma in agni chanting ' SVAHENDRASSHATRURVARDHASVA '. He wanted to create an enemy for Indra to destroy him. Due to a slight variation in the intonation he ended up strengthening Indra himself, Vritrasura came out of the agni. Eventually he got killed by Indra.
Moral of the story - Neo 'rishis' are distributing mantras as if drought relief supplies . Sanskrit is a language where precision is very important. One could end up with the fate of Kumbhakarna or Vritra.