You wouldn't be my slave, if that's what you're asking. But there is a contact involved.

[He waves a hand, and as he does, the umbrella overhead spins around and slowly transforms its shape into a pink bat with its wings spread. Folding them up, it chirps and hops along the back of the couch, until it can reach Mephisto's waiting hand to nuzzle against it.]

However, unlike a typical contract with a demon, when I employ a familiar, what I offer is far more akin to a partnership! In exchange for lending me your power when I am in need of it, I offer you my own power and protection as needed, as well as my trust and loyalty. I would never betray my own familiar, nor would I expect them to betray me.

[And he adds with a snicker--] And I suppose it would be rather fun were I to require you to call me "master" all the time.