One of the questions Artie suggests to ask when investigating artifact effects, "Do you smell fudge in places where there are no fudge?", becomes a bit of a running joke in the series. Midway through the first season, Myka uses the phrase "I smell fudge" to tell Pete that she's on the trail of an artifact; in the season two premiere, Artie identifies an invisible mine by smell, which Claudia immediately states is fudge.
There was considerable actor crossover between "Warehouse 13" and "Eureka'. Not only did Allison Scagliotti appear on Eureka as her Warehouse 13 'Claudia Donovan' character but Neil Grayston appeared on Warehouse 13 as his Eureka "Douglas Fargo' character. In addition Erica Cerra (Eureka's Jo Lupo), Joe Morton (Eureka's Henry Deacon) and Niall Matter (Eureka's Zane Donovan) appeared on Warehouse 13 as other characters. Cerra and Matter were husband and wife con artists and Morton was a prison preacher. Likewise Saul Rubinek (Warehouse 13's "Artie") appeared on "Eureka" as Dr. Carl Carlson.
Many of the aspects of the characters of Pete and Myka were influenced by their actors, Eddie McClintock and Joanne Kelly, respectively. For example, McClintock suggested Pete should be a former Marine and love comic books, and Kelly asked for Myka to love literature and be a book worm.
It has already been pointed out that Eureka crossed over to Warehouse 13 and vice/versa with the characters Claudia and Fargo. Warehouse 13 also crossed over to ALPHAS with the character Dr. Vanessa Calder (Artie's love interest played by Lindsey Wagner) putting all three shows in the same "universe".
Quite a few actors from the Star Trek world have appeared or had parts in the series. To name some of them: Robert Duncan McNeill, (Tom Paris from Star Trek: Voyager (1995)) directed an episode in season 5, Kate Mulgrew (Captain Janeway from Star Trek: Voyager (1995)) plays Jane Lattimer, Brent Spiner (Lt. Commander Data from Star Trek: The Next Generation (1987)), Armin Shimerman (Quark from Star Trek: Deep Space Nine (1993)), Jeri Ryan (Seven Of Nine from Star Trek: Voyager (1995)), and René Auberjonois (Odo from Star Trek: Deep Space Nine (1993)) also appeared. Also, Faran Tahir plays one of the Regents, Adwin Kosan, who was also in the Star Trek reboot as Captain Robau.