I believe there are three (3) types of Adult Babies and of course Diaper Lover:
An adult who enjoys drinking from a bottle, blankets, kissed on forehead, pacifier, diapers (messy and wet), formula, bubble baths, baby clothes, etc. Pretty much everything baby.
An adult who is a little older and enjoys drinking from a bottle but not really formula (maybe next steps, milk or juice), pacifier at times, diapers and pull ups (mostly wet and sometimes messy), bubble baths, some baby clothes, etc. Most things baby.
An adult who is older and enjoys drinking from a sippy cup, baby bottle as a comfort item or bedtime with mostly juice, milk or water, might hide the pacifier and use it from time to time, tucked in at night, loves pull ups some diapers (wet), loves bubble baths, toys all the way, not to much into baby clothes but would wear shortalls any day of the week. Some baby things.
(also may prefer being a big brother/sister to an adult infant or baby)
Just Diapers and nothing else. Put one on and let it stay.