I have a 7 month kitten. Had been playing with him for ten minutes when he suddenly started panting really heavily - he was running around like a mad thing chasing a stick. He still wanted to carry on playing and was very excited but I panicked as it seemed quite abnormal. Almost sounding like when a cat goes to cough up a fur ball - very noisy. Have taken stick away and he has calmed down - has hiccups though. He gets hiccups quite a lot as well, especially after eating, not sure whether that is normal either! Happy to be told I'm overreacting and it's normal - been a long time since I had a kitten!