Jason likes to brag about how he has no weaknesses, unlike the other bats. He’ll go on and on about it during training, mostly to intimidate them.
One day he had the absolute PLEASURE of bragging about it in front of Bruce while they were all watching t.v. on the couch. Bruce didn’t say anything, just calmly walked over and sat next to Jason, leaned over and cuddled him into his chest. Right before Jason had the chance to complain, Bruce’s hand slowly slid towards his belly. At that moment Jason had realized he fucked up.
Keep in mind that Jason is not ticklish. He never was, a life born on the streets hardens to you too much for that, but that one spot juuuuust to the right of his belly button? Makes him snort louder than a pig.
Back to our story, Jason is yelling profanities and threats in hopes to get Bruce to stop before his hand reaches its destination. He does not. He reaches the spot, taps it a few times experimentally, dramatically, and then tickles it.
Bruce has to hold Jason 100 times tighter to keep him from escaping. They end up rolling on the floor, Jason laughing involuntarily, struggling and swearing, when he gets free he punches Bruce’s smug face and storms out, red as a cherry.
Bruce had no regrets. All the batkids will never let Jason live this down.