This is on 'Flight into Terror', when Ted and Dougle travel on a plane. It occurs twice.

1. Note that behind Ted and Dougle are three other passengers, the middle one being ginger haired. When Ted presses the emergency button, and it shows the passengers, look at Ted and Dougle's seats. There are 3 older priests in them.

2. After the ending credits, when it shows the passengers again and the captain announces that the emergency is over. The old men are in Ted and Dougle's seats again.

Enjoy!