My son is being a little stinker for us and his ABA tutors. He messes up on purpose, waits for a response from us, says "try again" and then laughs. It's good that he is breaking his rigidity in this area, however I'm afraid it will slow his progress on programs. I have to laugh because he used to get so mad if you put something out in the wrong order. He started doing this with story sequencing cards and when he finishes he says "Look, I did it", but must have realized I wasn't always "looking" and started testing me. I know, bad mama. He has now started doing this in his other programs. They usually just wait him out and he self corrects in his silly way.
Cassidy has ALWAYS done this. For her it's mostly an OCD/routine, but sometimes it's a 'leave me alone' response. Clear back in ECI when she was two and wasn't really talking - she'd be cooperative & play their games, but ALWAYS did everything wrong once before she did it right. She doesn't do it for me anymore, but ANYTIME she's with a therapist or teacher, she'll do it everytime. It makes for tricky evaluations if they don't give her that 2nd or 3rd chance. & It's a big reason, mainstream school scares me because she's not going to care about a 'good grade' and they're not going to give her the 2-3 chances for her to give the right 'answer' she knows. :( She does this alot with her states/capitals. She's had them all memorized for a long time and is often treated like a circus act by people who 'know', well she doesn't want to be quizzed & has figured out if she gives the wrong answers, 'they' will quit asking. :p
ETA: She doesn't 'look or act' like she's doing it on purpose and definitely doesn't say she is, I'm not sure she realizes she does. Therapists have no idea until I tell them and now they give her the extra chances. It's just one of the quirks I've figured out about her along the way. She's too consistent at 'doing it wrong first' that it has to be intentional. The lack of acknowledgement from her is why I believe it's a 'routine'/OCD she's created that she HAS to do and not something she's doing FOR attention...
I say look at the positive, your son is developing a sense of humor! My husband used to do silly things like that with my son, and it really helped him learn to recognize that people sometimes do silly things for a joke, and the socially appropriate thing is to laugh. Why not try doing silly things with him, and then laughing with him. My husband used to tell my son he was going to give him camel lips for dinner. At first my son did not know it was a joke, but my husband would laugh and say something link, no, maybe dog fur, until finally my son caught on.