Wheaton is best known for his work in the film "Stand By Me" and on the TV series "Star Trek: The Next Generation."
The new season of "Eureka" is slated to return to Syfy on July 9.
"Wheaton plays the brilliant Dr. Isaac Parrish, head of the Non-Lethal Weapons Lab at Global Dynamics," Syfy said in a news release. "Parrish's dry wit and superior attitude make him a thorn in Fargo's side -- with potentially disastrous consequences."
Wheaton's episode is to air July 23.
Neil Grayston plays Fargo on the series.
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