The Flash to The Wire
4 connections
The Flash
Arrow
Arrow spun off The Flash
Law & Order
Hudson University is the fictional University where many Law & Order characters graduated as well as the location of F.I.R.E.S.T.O.R.M. On Arrow
Homicide: Life On The Street
Law and Order and Homicide crossed over on four episodes
The Wire
On The Wire (episode "That's Got His Own") Junior Bunk from Homicide was mentioned as someone who had once put bad drug product on the market causing deaths.