Really, he's not that surprised that Watson would ask that question and maybe he should be a little concerned that he has so many examples right at the tip of his tongue. The problem was which should he mention?

"I live with a famous detective and one of his 'clients'" He uses the word loosely. "invited us all to an amusement park and gave us VIP-um special wrist bands that would give unlimited free rides. We found out later there were explosives in the wrist watch and Heiji-niichan and Kogoro-Ojisan only had twelve hours to solve the case or else the client would detonate the explosive. It turned out okay, though I did end up breaking my leg." Don't be too worried about the flat and unmoved tone in his voice as he recounts the details almost like he's reporting on his day at school.