When she met the four of them, she swung her tail down reflexively without looking, and ended up throwing them all into the quagmire, leaving them all in a state of embarrassment.
Because he was bored, he agreed to Ravenclaw's invitation and became the Potions Professor at Hogwarts, but he never expected that he would stay at Hogwarts for thousands of years.
Salazar Slytherin, when they first met, he was thrown into the quagmire by her and his whole body was covered with mud. That was the time when he was most embarrassed. He looked over angrily, but she kept laughing not far away.
He did not object to Rowena's invitation to become Potions Master, not knowing that this decision would later lead to her stealing his heart.
When he realized that he could no longer escape, they met a thousand years later...