Pull it/something out of the bag
Definition 1 of 1
Pro Tip 1/3Unexpected Success
Use when someone succeeds against the odds, when no one thought they would. 
Everyone doubted her, but she pulled it out of the bag and won the competition.
Pro Tip 2/3Last Minute
Especially useful for describing a sudden success near the end of an event or time period. 
He pulled it out of the bag with only minutes left in the exam.
Pro Tip 3/3Implies Tension
Often suggests a tense or challenging situation where the outcome was uncertain. 
With the deadline approaching, they pulled it out of the bag with a brilliant proposal.