When Barnabas saves David from the falling disco ball.
In general, anything Barnabas does to look out for David. There's the part where he discovers that David's father is having an affair. Barnabas is furious and tells the father that either he does one of two things, or Barnabus will expose his secret. The first option is to snap out of it and be a good father, like David deserves. The second is to take money that Barnabas gives him and leave. It sadly doesn't end well when the father chooses the latter option.