City of Crime, Tom Hanks and Dan Aykroyd's ill-advised but endearing end theme to 1987's Dragnet. But in many cases you're simply staking a claim in bizarre territory when you draft an actor to sing your theme song. Earlier in the 80s, Wings Hauser's truly stellar turn as killer pimp Ramrod (yes) in Vice Squad was so dominating that he (Hauser/Ramrod) sang the movie's indelible theme "Neon Slime". Hauser's vocal instrument isn't exactly Juilliard-trained, but he attacks the track with gusto, tightening Ramrod's grip on our imaginations as we leave the movie, concussed.
Dennis Rodman is deployed like a flamboyant special effect through much of Double Team, so it's no surprise that he raps over Crystal Waters' end theme to the movie. In this track Rodman may be reprising his character from that movie; Ices T and Cube are certainly rapping in character in their end theme to Walter Hill's Trespass. But LL Cool J truly goes large in "Deepest Bluest", taking on the character of the sharks from Deep Blue Sea. (The bizarre promo video for that track, which initiated this blogpost in the first place, truly must be seen to be believed.)
This is not to say that all such end songs are deployed to silly ends. Clint Eastwood's frail vocals on the closing title song playing over Gran Torino's end credits provoked some derision, but the sublime completion of the song by Jamie Cullum nicely mirrors the movie's passing of the torch from one generation to the next. And recording artist Jay Chou has been drafted for end themes for his movies from both sides of the Pacific; he had something of a hit for his end theme from Zhang Yimou's Curse of the Golden Flower, and though not composed for the movie it closes, Chou's "Nunchucks" provided a fine capper (and restored some luster) to the otherwise problematic movie The Green Hornet. (I'm reminded of Nicolas Cage's final serenade in Wild at Heart, which technically qualifies.)
As long as studios squeeze every cent out of their movies that they can, we can expect these curious songs to continue. It's easy to think of a few movies that might have been improved by such songs. A friend who wasn't down with The Departed suggested that DiCaprio and Wahlberg could have freestyled over the closing credits, and the idea's too good to shake. Who'll be the next actor to step up to the mike and go that extra mile?
Just as crucially, why the hell didn't Ice-T's songs about Dick Tracy make it into the movie?