Muddling up my words

With a dose of ditziness and tiredness I often get words muddled. Here's some recent crackers:

• Calling the kindle I'd bought my mum for her birthday a kimble (I think that's a better name!)
• Referring to hovercraft parenting - instead of helicopter parenting
• Yesterday I tried to describe a small bag I need for my bicycle to the man in the v.professional bicycle shop. He had to ask many questions just to get the right type of bag, must of thought I was a little mad.  

I think son 2 has inherited this characteristic (maybe its not down to sleep deprivation and too many balls to juggle) as he often gets his words muddled. Today he wanted to be caper-sized in the swimming pool rather than capsized. Poor child, his older brother often takes the p**s. What words do you get mixed up?