1. I didn't know when the fireworks were on because I hadn't checked the programme.
2. When we got to the gate I discovered I had forgotten to bring my ticket.
3. I bought the T-shirt when the band had finished their act.
4. After we had put on our costumes, we joined the parade.
5. The parade stopped because a float had broken down.
Ответ: 1. hadn't checked; 2. had forgotten; 3. had finished; 4. had put; 5. had broken.