Christmas

Can Christmas be celebrated in Souls IC?

Sure; there have been characters in the past who celebrated Christmas or even observed Christian-like religions. An alternative to Christmas might be the celebration of the winter solstice, which is more "accessible" for canines to know about. :)

Short answer: Sure.

Long answer: Sure, but it's worth considering why a given canine would know or care about Christmas specifically. It is not improbable for Christianity in some form to have passed from humans to dogs and from dogs to greater canine populations, and some of the traditions of the religion, such as Christmas, to have survived this way. That said, a canine view of Christ may vary significantly from a human's and religions do change naturally as time passes through variations in teachings, in interpretations, etc, so the "meaning" of Christmas to a given canine may be considerably different from a human's.

As Sunny said, winter solstice may be more "accessible" to a given canine since there isn't as much cultural history attached and there aren't any specific traditions, per se.