If someone says Happy New Year, you say Happy New Year. If someone says Happy Diwali, you say Happy Diwali and with the same logic, if anyone says Happy Birthday, you way Happy birthday. Manu kept wishing everyone a Happy Birthday who wished him on his third birthday. We kept telling him he is supposed to say Thank you but I guess he liked Happy Birthday better. At school too his teacher exclaimed “He is saying Happy Birthday to me!” They made him feel really special and he was quite happy with all the attention.