At the end of Series 2, Ricky asks Karl if there's anything he didn't do that he might have, had he done it again. He says that he would have quite liked to do some karaoke in Japan, singing some Chas And Dave. Cut to Karl recording There Ain't No Pleasing You, with Chas And Dave. It's impossible not to smile at just how happy he is.
After meeting the transgender women in Bangkok, Karl muses about how he'd react if he found out Suzanne was 'actually a bloke' and concludes perhaps he wouldn't mind. Think about that for a moment. Karl, a man who can barely understand other cultures and identities, to the point where he couldn't believe that an Amish community didn't know who James Bond is, is so fond of his girlfriend he wouldn't mind if she turned out to be a man. Awwww... (Still, Karl being Karl, he says would expect her to pull her weight a bit more and carry heavy shopping with him).
In Series 3, Karl and Warwick Davis had a genuine heart to heart moment when Warwick was having difficulties climbing the stairs of Mount Emei and after their moment Warwick pushes through and reaches the top of the mountain. Just seeing how the usually pessimistic and grumpy Karl having a You Are Better Than You Think You Are talk with Warwick just warms the heart, even though they still snipe each other and argue.
In Series 2, Ricky calls Karl in Alaska to angrily ask him why, in his physical, they didn't let him check his prostate. He concernedly goes on about all the men who die in the UK every year from prostate cancer, and many subsequent calls touch on this topic, trying to convince Karl to get checked. Ricky and Steve finally badger him into it in the last episode of Season 2, Ricky giving the reason that he's his "best mate" and he genuinely wants to make sure that he's healthy with a quick (though on Karl's part, squicky) test.
In Series 2 when Karl is in Japan, he experiences the Japanese tea ceremony. Although he makes a little joke at first, he ends up liking it because it turns the drinking of tea into an event, and he is able to connect with the other participants over their love of tea, even though many of them couldn't speak English.