Hopping Vampire

I had a villain with a cream pie power like that.  A standard drain on Presence.  It did not flash, it instead made you look so stupid you had a hard time doing presence attacks.

With HERO it is all about the game effect that you want to achieve.  If you throw a pie at an opponent, what do you want to happen?  Ignore the special effect at first and focus on the game effect you want to achieve.  
 
As Oruncrest said, an obvious game effect from throwing a pie might be rendering someone unable to see for a short time (we use Flash to achieve that).  You might want other stuff, like it enrages the target or embarrasses him or something else.
 
The coming apart routine is a complication (if you are not really trying to simulate being chopped up and healing).  I would have a complication that indicates that when you are successfully attacked by a slashing weapon you suffer some kind of "separation" with resultant disabilities (head means you have a different perspective with regard to your body; arm means you have only one arm to use, etc) until you spend a phase with parts in the same hex...
 
Doc

Throwing Pies would be Flash.
Seltzer Water would be Flash again, but this time with double knockback (+3/4 to base cost).
The Banana gag would of course be Change Environment with Luck & Unluck changing the odds.
The Mochi Mallet would be a straight Blast that does no BODY to living beings (-0).
Finally, the 'Off With His Head' routine is LOTS of Resistant Defense with the Limitation Susceptibility: Change Environment (Stunned for as many phases as the attack had D6 plus 1 (Hop can recover if an ally assists him for a phase).
 
Hope that helps