Not Age Appropriate

I work with mentally retarded adults. We are encouraged to find them age appropriate activities. However, many of them stopped their mental progress at a certain age. One of the men I work with is still a kid. He wears Mickey Mouse ears to work because he wants to be like Jimmie Dodd of the Mouseketeers. He also wears a clip-on tie because Walt Disney, his hero, wears a tie. I humored him today and had him teach me the Mickey Mouse song. "M - I - C, see ya real soon, K - E- Y, why? because we like you! M-O-U-S-E!" It might not have been age appropriate activity for a 50 year old, but he still wants to be a mousketeer.