Middle Child Syndrome?

According to the Urban Dictionary (which is where you learn of all things hip and happening), Middle Child Syndrome is defined as (and I'm quoting here, because it's important you understand this right):

When a middle child - typically of a family of three kids who are close in age - feels left out or neglected.

Because the bigger sibling is the first born and typically an over-achiever, they are the most important and get the most privileges. A younger sibling is the 'baby' of a family and gets away with more as well as being the most looked-after. Middle-child syndrome starts when the middle child is squeezed between these two and have trouble finding their 'niche' in the family.

Middle children will sometimes...
- misbehave to get attention
- go with the flow
- work as little as possible
- be less parent-dependent than their siblings
- become the 'loner' of the family, not participate in family events unless told to
- play the peacemaker
- be more likely to go to a friend for advice than a parent
- be very creative
 
There must be a third child in my future somewhere, because this description above has Sam written all over it!

What feels like overnight, Sam has become this super-independent, head shaking (he may not speak much, but sure can tell you "no" without any confusion), schedule-defying, rule-breaking bundle of unbridled energy and mischief. And while it can be lots of fun (in really small doses), it's also incredibly exhausting!

This week has been particularly so: I have found him, fully clothed, in the shower at least three times; I have had to fish out toys, Tupperware, and for the first time Zac's (clean) school uniform from the toilet; In his fierce resistance to bed time, he has taken to jumping on the bed in the dark, and twice jumped onto Zac and right off the bed; And even though it's the middle of Winter here, the other day I found him stripped to his diaper and jumper, sitting playing in a muddy puddle...

Does anyone know where my sweet and serene little baby Sam disappeared to - and if so, can you please send him back?!