Fetty Wap -- Like Hey What’s Up Hello ... Kansas City Royals (VIDEO)

Fetty Wap’s “Trap Queen” and the KC Royals are like Reese's Peanut Butter Cups -- and since the players have turned the song into their unofficial summer theme ... Fetty paid 'em a visit.

The Royals have been playing a game where they work "1738" -- the opening lyric to Fetty's hit -- into all their interviews. Anyone who fails gets fined in the clubhouse.

Guess F-Dub caught wind of this, and dropped by Kauffmann Stadium on Tuesday evening to check out the Royals' skills, and to jump them into his Remy Boyz 1738 crew ... with t-shirts.

Warning, Alex Gordon ... do NOT let Fetty introduce you to the stove.