LOL... I was the opposite, I was a total cheapskate when I was spending someone else's money (albeit on a budget).
When I was a kid, one of the department stores had a special section set up for kids to do Christmas shopping. The parents could provide a list of who they had to buy for, and a total budget and payment method. A store clerk would take each child into the section, help them shop, and if there was a credit card for payment, run the receipt out for the parents signature.
I was given a budget of $50. I spent $26.
Of course, I was also the child who refused to spend any dollar denomination higher than $2. $2 and $1 and change I would spend. Anything higer was sacrosanct and stayed in the piggy bank until it went to the bank. No idea where I got that from.