Date: March 22, 1991
The Moment: In 1991, Teenage Mutant Ninja Turtles II: The Secret of the Ooze was the smash of the summer. Helping its success was the presence of a rapper quite popular in his day, a Caucasian fellow better known to the world at large as Vanilla Ice, who performed his "Ninja Rap" in the middle of the movie, as part of the plot, assisting the Ninja Turtles in their fight against these guys.
The Impact: The move raised Vanilla Ice's profile...among kids. It certified him as a pop star who managed to hang onto his moment, but took a severe toll on what little credibility he had with anything remotely resembling a "rap" audience. The film, however, grossed over $78 million at the box office.
The Upshot: The Ninja Turtles eventually feel out of popularity with young people in favor of Power Rangers, and then, Pokemon. Before then, they'd make two more films, one in 1993, and the next one in 2007 (which was entirely animated). Not only was Vanilla Ice in neither of them, but his own film, Cool as Ice, released just five months later, was a box-office bomb. Ice's career went downhill from there: Drug problems, money problems, and issues with having a "harder" sound—or any sound, really—taken seriously. He had a brief nu-metal rap-rock revival in the late '90s, only to eventually suffer the pitfalls of fleeting fame again. After an independent release here, and an independent release there, Ice is now featured on a reality television show about flipping houses. Despite all of this, Ice still finds appearing in the Ninja Turtles movie to be "one of the coolest experiences of his career," which is funny, because it acts as a cautionary tale for any rapper who ever looked to cash in with too wide of an audience, too early into their career.