Very straight-forward. The Spirit Bear cannot be affected by the Cripple of Lycan's wolves. It is the only non-building, non-ward unit which is immune to it.

Repro:
1. Pick Lycan and level up Summon Wolves
2. Summon the wolves
3. Attack an enemy Spirit Bear
4. Observe its status bar

Result: Cripple does not proc at all.

Expected: Cripple should work against the spirit bear normally.