no I never had alters that would laugh inappropriately.

all my alters were trauma / dissociative related.

By that I mean the dissociated parts of me were caused due to extreme trauma before I was 5. They held traumatic memories / emotions and events of the trauma's. they were dissociatively stored in my unconsciousness. So I was never aware of what they were doing, saying and so forth until integration (the sharing of information, their existence and so forth).

Because of how DID was for me, trauma/ dissociative related I would experience something triggering, then have my dissociation symptoms, and then my brain through the flight or fight response process switched my behaviors, thoughts and so forth to that of the unconsciously stored parts of me (what others call alters)

Since those parts of me were trauma dissociative related they didnt contain things like laughter. their thoughts, behaviors, memories and so forth was that of all the trauma's that were dissociated.

That said when I was fully grounded (not a part/ alter) I did and sometimes do have a nervous response of inappropriate laughter.

Now we cant say whether ..........you............ have dissociated parts of you that laugh. for that you will need to talk with your own treatment providers. they will be able to explain to you what your parts/alters are and whether you were dissociated at the time you had your burst of laughter in therapy based on the therapy conversation, your triggers related to your dissociation symptoms and more.