My 4yo son had bell's palsy a ~year ago. Everything is fine now, but occasionally his eye deviates. Is there a reason he goes cross-eyed somtimes?

Unrelated phenomenon. Bell's palsy affects the seventh cranial nerve which is responsible for things such as motor movements of facial muscles, some control of the upper eyelid, control of tension on the timpanic membrane in the ear, and tearing. Eye deviation is not related to any process having to do with motor function of the seventh cranial nerve. Check with your child's pediatrician for further evaluation.
Deviation of eyeball. His eye abnormality has nothing to do with bell's palsy --- a year ago. Need to see pediatric ophthalmology coz by 4 yrs of age he should not be doing it!
Double vision / Bell. hmmm. Which way does your son's eye deviate? Does it matter if he tries to look from side to side when this happens? Bell's palsy does not affect the motion of the eyes. If you can clearly see this happening, it is a good idea to return to the friendly neighborhood neurologist.