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]
(..) -What have we done? -Great! Now I have guilt. We're almost there! Rocky, the ramp! Look out! Quick! Hold onto my tail! -Attaboy, Slink! -Oh! Woody! Woody! Speed up! -Speed up! -The batteries! (..)1995 Toy Story