Meg gave him that nickname and he's using it so people don't think Cas is his real name!

Ok will do a cheese burger I will make cookes dinner * and what about Cass why did he change his name that I. Notice that

I think maybe a burger will do like a yummy cheese burger I'm in the mood for that did you? See that Cas named him clearance

Ok Sam we will get her because she's a witch and she can help us Sammy I'm gonna make us dinner maybe spaghetti 🍝?

Smiles* back says Dean I'll let you help thank you for asking I'm a bit tired and hungry there's a lot of paper work but we got to worry about abandon she's not good person maybe Rowena can help us

Cas all you do is blab all the time ..