He was happily playing in the box, so I let him. A short time later, Jacob woke up from his nap (probably from the hysterical giggles from Luke) and of course, he just had to join Luke in the fun.
They seemed happy (and getting along) so I left them to play for 2 minutes (literally) while I finished up some dinner preparations. The giggling and squealing started getting a bit out of hand, so I decided to investigate. This is what I saw.
Needless to say, the cleanup was not easy, but the boys had a blast, so I can't say I'm sorry I let them have their fun.