Taylor Swift is not part of Drake's regular circle.

So she was a somewhat surprising participant in Drizzy's big 30th birthday bash in LA on Sunday.

To make her feel more at home, Drake showed her around. He also introduced her to his mom.

Hmm. Drizzy and Taylor are arguably the two biggest pop stars on the planet. And they are each just off high profile break ups  ....

While there were reports of Drake and Taylor getting snuggly at the party, sources told TMZ that the calculating celebrities are just friends.

Don't be surprised if they become something more -- if that's what the marketing data says they should do.