What to do with this leftover apple crumble and custard that's been in the fridge for a few days and has gone quite soft?  Well... I think we all know the answer; use it as gunge!  I pour down the front and back of a cheap pair of jammers, then drizzle some cocoa powder mixed with cornflour over my body, smearing it for added fun!
As it turns out, it's a fun substance to use as it's so thick it doesn't leak easily. It's also better when warmed slightly.