Is it weird to call a guy that isn't my dad and that I'm not interested in "Daddy"?

I've kinda been wondering... This man is 41 and I babysit his 1 year old daughter. Everytime he walks in the room she yells "Daddy!" And I thought it was funny to do it as well so everytime I see him I yell "Daddy." And as of late when I talk to him I'll call him Daddy but I stopped recently now realising that it is kinda weird. I do the same to her mom and say things like "Mommy, my passie?" I still do it to her mommy... but now I think it's a bit weird to do it to her dad. It it weird?

Is it weird to call a guy that isn't my dad and that I'm not interested in "Daddy"?
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