You were Rowena's familiar. As she was currently staying with Crowley, cozying up to him and trying to gain power in hell, that meant you were staying there too, which meant Crowley had to put up with you.

"Keep in mind, I hardly put up with my mother's presence," Crowley told you, as you changed back into your human form after doing cat things (like knocking things down). "I put up with yours even less." After all, weren't you the one thing his mother loved?