In the video Big Bucket Pussy, you might have caught the moment in which Serena tries to fist herself, and then eventually gets it with Leo's help - This was in fact Serena's first time fisting herself!

Here is the full version of that moment - The Behind the Scenes look at Serena getting her hand in her pussy with Leo's coaching. And yes, she got her hand in past the knuckles - a crucial distinction in our humble opinions ;)