These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
There was a literal special-effects failure on the set. The day before the crew was set to "destroy" the London of 1960, they made a huge batch of oatmeal, which would stand in for the lava flow. Unfortunately, there came a very hot day, which caused the oatmeal to ferment! It no longer had that thick consistency, but the effects team had to just roll with it.
Tear Jerker: Filby senior's ultimate fate. It's made even worse in a short film done for a DVD release of the movie in which an older George returns and meets Filby right before he leaves for the front. He tries to warn him, expecting to be disbelieved. Filby does believe him... and he goes anyway.