The Law & Order Star You Likely Missed On ER

The list of scripted primetime series that have been on the air for 20 years is understandably quite short. The list for shows that have gone 25 seasons or more is indeed even shorter (per Daily Infographic). It's becoming more and more likely, however, that "Law & Order: Special Victims Unit" will soon join the likes of "South Park," and "The Simpsons" in the quarter-century club. And when it does, "Special Victims Unit" will be the first live-action scripted primetime series to cross that impressive marker. 

The beloved series recently aired its 23rd season of stark procedural drama on NBC, and it appears set to deliver more "ripped from the headlines" stories for years to come. That fact is particularly impressive as "Special Victims Unit" is, and always has been one of the heavier shows on television. It's even more impressive when you consider the show has been anchored by star Mariska Hargitay for the entirety of its small screen run. Hargitay has now portrayed NYPD Detective (now Captain) Olivia Benson in a staggering 517 episodes of "SVU." 

You may not realize it, but "Special Victims Unit" is not the only long-running NBC drama Hargitay has appeared in over the years as she once had a recurring role on "ER." So too did one of her frequent "Special Victims Unit" co-stars. Here's which one. 

Donal Logue had a recurring role on ER years before joining the cast of Law & Order: SVU

The "Law & Order: Special Victims Unit" star that shares a past on "ER" with Mariska Hargitay is none other than Donal Logue

The actor was, of course, revered as one of Hollywood's most prominent "That guy!" types (per Rolling Stone) long before joining the cast of "Special Victims Unit" in 2014 as NYPD undercover specialist Lt. Declan Murphy. That status has only continued to grow with every appearance since. The most recent Declan Murphy sighting came in a Season 23 episode that reveals he's no longer working undercover, and instead heading up the NYPD's Hate Crimes division. It's also revealed Murphy is indeed the father of Det. Amanda Rollins' (Kelli Giddish) daughter, so we'd be very surprised if he doesn't make his way back into the "Special Victims Unit" fold somewhere down the road.

As for Logue's "ER" role, it was also in a recurring capacity, and it came much earlier in the actor's career. In fact, his first appearance as flight nurse Chuck Martin came in 2003. It initially added a touch of light-heartedness to the show too as Chuck was revealed to be the husband of Dr. Susan Lewis (Sherry Stringfield), whom she'd impulsively married on a trip to Las Vegas. The marriage was ultimately annulled, but the pair kept their relationship going and eventually had a child together. Logue's time on the show ended late in Season 11, but the role remains arguably one of the best from his pre-"Special Victims Unit" days.