I got uncontrollable giggles watching Dancing on Ice last week when they did the Oliver! routine. Same thing happened on Strictly when Chris Ramsey did it. It was the song.
At school aged 9, we did a performance of Oliver! A handful of boys decided to change the words somewhat and sang it all the time. To the extent that they forgot the real words and sang the silly ones instead:
Have Intercourse! At Home!
Have Intercourse! On top of the Furniture!
I still laugh now. And if I think about it I start creasing up which can be embarrassing. Especially if I have to explain why. I am giggling now writing this.