My (then) 7 1/2 month old was fascinated by him. He loves Mickey Mouse Clubhouse, so he got all excited when he realized who it was. This was also his first character interaction, and it definitely didn't traumatize him or anything (we have great photos of him with his hand on his pal Mickey Mouse's shoulder). In fact, he really enjoyed all the other character interactions afterwards.
However, Mickey said something along the lines of he should enjoy being carried around now because before he knows it, he will be grown up and needing to get a job. DH and I found that a little weird, but we look forward to telling him that Mickey said he needs to get a job in the future.