NCIS/SVU crossover, only sort-of-not-quite. Basically, the premise is this: Brian Cassidy, at some point after switching from SVU to Narcotics gets involved in a case down in Baltimore, works in tandem with Tony (with the Baltimore PD) and Gibbs (with NCIS. (Note: case will have to involve death, drugs, and the Navy in order for all required parties to be there.) Gibbs gives both Tony and Cassidy a job offer. Hijinks ensue.
Timeline I'll be using if I write this: June 2003 - Kate starts at NCIS March-May 2003 - Viv Blackadder works at NCIS January 2002-March 2003 - Cassidy works at NCIS January 2002 - Tony starts at NCIS March 2000 - Tony starts at Baltimore February 2000 - Cassidy switches from SVU to Narcotics June 1999 - Abby starts at NCIS