At two months shy of five years old, my daughter is pretty good at speaking correctly, but she does still sometimes have trouble with irregular forms. At times like that I have to choose between letting it go and offering her the correct form. Sometimes, though, I do this instead:
Apo (in Slovak): Actually in English it's one 'mouse', but two or more 'mice'. It's irregular.
Me (in English): Yeah, and it's one 'house' and lots of 'hice'.
Apo (shaking head, to K): Houses.
Me: And one 'louse' and lots of 'lice'. Ooh, and one 'rouse' and lots of 'rice'.
Apo (to me): Wait, really?
Ha! I got him.
This week K had her first ballet lesson. She loves dancing, pink, princesses and anything girly, so she was PUMPED. A day or two before, the Slovak told me she prayed at bedtime "...aby na mě nic neskočilo, abych nebyla nemocná a mohla jít na balet." (so that nothing jumps on me so I won't be sick and can go to ballet) After a minute he realized she meant "aby na mě nic nelezlo" (climbing, not jumping), from něco na mě leze (I'm coming down with something).
You probably have to speak Czech to find that very funny...