Because he was expecting to meet Iron Man instead.

This has clearly never happened to RDJ before.

18 month-old Jaxson Denno's mom explained that the little guy was confused because he was expecting to meet the Iron Man in the infamous armor. Downey was in Massachusetts filming The Judge.

Source: Heather Denno  /  via: dailymail.co.uk

But it all seemed to work out okay.

Source: Heather Denno  /  via: dailymail.co.uk

They even got this (slightly disinterested) group shot.

Source: Heather Denno  /  via: dailymail.co.uk