Surprise moments has been a running theme throughout Summer Jam's history, the most memorable being Jay-Z bringing out Michael Jackson for "Izzo [H.O.V.A.] in 2001. This year, celebrating the 20th anniversary, was no different.

Though it was raining at Summer Jam XX, and eventually lightning shut it down just moments earlier than expected, the biggest thunder still came from the crowd when French Montana wrapped up his closing set with "Pop That" and brought out Rick Ross and Lil Wayne.

Earlier in the evening, the YMCMB crew also repped with Nicki Minaj, who gave DJ Peter Rosenberg a hug — making the peace official. She joined 2 Chainz for his "I Luv Dem Strippers" and "Beez in the Trap."

The return of the YMCMB superstars comes a year after they boycotted the concert due to Rosenberg's pre-show comments about Nicki's "Starships" single.

More surprising than her performance, however, was the non-drama that was her presence. There were no reported run-ins with Lil Kim, who came out with fellow Brooklynite, Fabolous; or with Mariah Carey, who came out with Miguel (who came out without any leg-dropping).

Foxy Brown was also on the premises. She was to come out with Fab as well, but timing was off (reports have it that she was late and that Fab's set was cut short) and she was left backstage, upset.

The Wu Tang Clan, who were there for the first Summer Jam, came out to school the youngsters in the crowd. "We came to remind you of '90s hip hop," Method Man said.

But it was the youngsters on stage that were the most surprising.

A$AP Rocky brought out Bone Thugs-N-Harmony; and Kendrick Lamar led a sneak attack when he allowed Papoose on stage to perform a song and a "Free Remy" chant. (His wife, Remy Ma, has been locked up since 2008 and, according to him, is expected out next year.)

Hot 97 Program Director Ebro Darden was so thoroughly confused by the Pap addition that he tweeted, "Yo @Papooseonline call in tomorrow.. U thought that was dope? U think that helped get ya music hot? Let's discuss.. Send #"

On the radio this morning, Rosenberg revealed that he had talked to K-Dot prior to the show (but failed to mention anything to Ebro). The West Coast rapper told the DJ that he wanted to show similar respect to what Pap had shown him earlier in his career.

"I'm not mad at that," Ebro said before giving Pap's performance song a spin. "But," he said, "if anybody tries that ever again, I'm cutting you off so fast." 

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(Photo: Johnny Nunez/WireImage/Getty Images)