André Castagnetas is the agen codenamed X-101. The codename "X-101" dates back to the early 1960s and is part of the Departement "X" (X Division) of the European Union with agents numbered X-101, X-102, etc. The X-101 codename was used by other agents before Castagnetas. X-101 works with a teenager named Squitt and a pet tiger, Sultan. His favorite cover is to pose as a gipsy, traveling along in a caravan.
X-101 assisted Jean Sten against Wampus, and was present at Phenix's "funeral". He also fought Jaydee when he threatened Paris and recently helped the Strangers and the Guardian of the Republic against Salamandrite No.17..