The animal constituent in Celebrations is Whey rennet from Calf. Whether it is from an animal which is slaughtered according to Islamic rites or not the calf rennet in the opinion of some scholars is Permissible.

It is permissible to eat cheese which has rennet from calf rennet though praiseworthy to refrain from due to a slight difference of opinion. For those who wish to refrain a key is adopted to show which items has animal rennet.
Whey sourced from calf rennet is acceptable:

Is Whey Rennet Haraam? (no!)
http://gmwa.org.uk/foodguide2/viewquestion.php?foodqid=20&catID=1&compID=1

MARS Confectionary 2005
http://www.gmwa.org.uk/foodguide2/viewquestion.php?foodqid=159&catID=2&compID=2