Ken Griffey Jr. -- SOMETHING'S FISHY ... In New Macklemore Video

So, when Macklemore throws "fish to a player" in his brand new music video ... turns out the "player" who catches it is none other than The Kid himself, Ken Griffey Jr.

Griffey has a super brief cameo is the new Macklemore video "Downtown" -- wearing his old Seattle Mariners uniform.

Of course, Macklemore's from Seattle ... loves Seattle ... and with Griffey's history with the city, it's really not THAT big of a surprise he's in the video.

No Ichiro or Randy Johnson though? Maybe next time ...