It takes perfect circumstances to lift Obi-Wan’s usual sardonic expressions into ones of true mirth.
The first time since he was left at the Temple was also the first time he started talking again. It had been Master Yoda that finally broke through, and that was via a few pranks on some of the Council. Obi-Wan erupted into giggles while Yoda winked conspiratorially, inwardly relieved that he finally got the youngling to relax a bit.
Fast forward to his apprenticeship with Qui-Gon. The elder Jedi was growing concerned by his padawan’s stoicism. He had been reassured by some that this was normal Obi-Wan behavior, but surely he did more than quiet chuckles and witty comebacks? Still, Qui-Gon went through his entire arsenal of bad puns, pranks, and anecdotes until finally, one day, he heard Obi-Wan burst out into full laughter at the very rare sight of Qui-Gon completely bald. It warmed Qui-Gon to know that he was indeed capable of laughter like that, but it wasn’t enough to stop him from growing his hair out. Fast forward again to their mission on Mandalore, and Qui-Gon was torn between seething and bursting into laughter himself. How was it possible that the Duchess was able to do in two days what took him six months?!
Anakin was both confused and worried. He knew that Obi-Wan was still taking Qui-Gon’s death rather hard, but did he never laugh? Others around him (when they bothered to acknowledge his presence) informed him that this was normal, but Anakin wasn’t certain. Like Qui-Gon, he set out on a mission to get a full round of laughter from Obi-Wan. His actions seemed to make Obi-Wan even more morose, but after a few weeks of his attempts Obi-Wan sat him down and told him each and every single time Qui-Gon tried to make him laugh properly. Halfway through the night, Obi-Wan was nearly in tears from laughing so hard telling Anakin some of Qui-Gon’s antics.
In another life, Carwyn laughed much freer than Obi-Wan ever did, and at almost everything. Even more so when he met Beau.