pastortdtyson said
Is there are a relationship between Christianity and Worshippers of Serapis? 

  

Later on, second century onward, there seems to have been a syncretism between Christians and the Serapis cult, however, there is nothing before the second century, and even evidence from the second century is sparse and debatable. The Historia Augusta has been occasionally claimed by mythicists as evidence that Jesus was based on the Serapis cult, but the Historia Augusta is a forgery from the fourth or fifth century so it doesn’t aid anything.

Ultimately, the relationship is slim and just like any other ancient cult and Christianity. A syncretism between two different religions.