(Sometimes children think old people have been old all their lives and that old is not something they can ever be themselves. But old people were young once of course):

Once old people were totally cool
Once old people used to play football

Once old people had no aches and pains
Once old people had fashionable names

Once old people used to jump and run
Once old people were not grandads and grandmums

Once old people went to school every day
Once old people were not wrinkled and grey

Once old people were shiny and new
Once old people were as old as you