When the crowd responded to the show so positively, we realized we were 'onto something'. [=we had done/discovered something important, special, etc.]
Scientists believe they are 'onto' something big. [=scientists believe they are close to making an important discovery]
Don't try to shift the blame 'onto' me. [=don't try to blame me instead of the person who should be blamed]
(..) - Yeah, sorry, lady. There's no time. - . You should sweep me off my feet... out yonder window and down a rope onto your valiant steed. You've had a lot oftime to plan this, haven't you? Mm-hmm. But we have to savour this moment! (..)2001 Shrek