The creators of the Philadelphia Phillies' famous mascot, the Phanatic, are threatening to take it away from the MLB team ... and now, the Phillies are fighting like hell to keep it.
It's all spelled in a new lawsuit obtained by TMZ Sports ... where the Phillies say back in 1978, then Exec V.P. Bill Giles had a vision for a "green, fat, furry, big-nosed" mascot -- and they worked with a design firm called Harrison/Erickson Incorporated to make the Phanatic.
The MLB team says everything went smoothly with the negotiations ... it paid the firm for its work and the character was an immediate success.