Well what do we have here? It looks like Princess Celestia and Luna have decided to test the endurance of the mane 6, the elements of harmony. By tying their arms in front of wooden poles and tickling their feet for 1 hour.  
here are their reactions.
 
Twilight: D…Dear Princess Celestia..I learned that m…my feet are way too ticklish!!! HEHEHEHEHE!!!!
 
Rainbow Dash: BWAHHHAHAHAHAHA!!!!!!! OH MY GOSH!!! I CAN’T TAKE IT!!!!!
 
Rarity: NO!! NO!!! NOOO!!! Not the feet!! anything but my feet!! HAHAHAHAHA!!!!!!!!!
 
Pinkie Pie: I may enjoy laughter, but this is pure torture!!! HEHEHOHOHAHAHEHE!!!!!
 
Applejack: A’h must not break!! but ma feet are soooo ticklish!!!
 
Fluttershy: HELP ME!!! SOMEONE!!! KEKEKEKEKEKE!!!!!!!!
 
Here are their shoe sizes and footwear. FYI you can see what their footwear actually looks like in my previous tickle torture pics involving the mane 6.
 
 
Twilight: 8 Black Short Boots and black socks.  
Dash: 9 1/2 Blue and red tennis shoes and black socks  
Rarity: 8 1/2 White high heels  
Pinkie Pie: 9 Brown Flip Flop sandals  
Applejack: 10 Brown Cowboy boots and white socks.  
Fluttershy: 7 1/2 Yellow flats.