Here we go again...
I've heard this so many times before. It's been done many times before and will be done many times more.
You'll probably find in the end it was an 152 Aerobat or something.
ANY and EVERY aircraft (excluding obvious exclusions) will loop, barrel roll, aileron roll, stall turn etc, etc and such manevures are probably within most of these aircraft's g limits, however as there is usually little margin in the certification limits, it is not advisable.
I know people who have looped 172's, Jabiru and an Aerostar and are still alive to tell the tale and will probably never come unstuck, but one day, someone might fall out the bottom of a barrell roll and end their life because the aircraft wasn't designed for it. Not a good result.
(Sorry to steal Michael, however it's a great gif)