面白いつくりの部首： 可 （か）。

I was just looking up the derivation of 過 (su.giru, KA) in ヘンシャー先生の書いた漢字についての本, and I noticed a string of kanji with the tsukuri radical 可 that share the reading カ.... Henshall says 可 is a twisted reed coiling to the surface of water, plus a mouth, and then in general it means a long time before speaking, with associated meanings of approval (grudging approval, permission, etc.)....

珂 with 玉 gyoku as hen radical, it's a jewel

河 with さんすい, three water drops, it's かわ kawa, a river or stream (same reading as 川; how does the meaning differ with different kanji? a less wide stream?　a particularly winding stream, as opposed to a straight-flowing river? just for fun, I Google image-searched each of the kanji; that didn't get me anywhere, but I did find this photo of a crab wearing three watches. time well spent!)

歌 Stacked with ketsu, a gaping mouth/yawn/lack, it becomes うた uta, singing/song. Henshall says the stacked カ may also derive from かか "ka ka", a Chinese version of "tra la la"—so, a gaping mouth going "tra la la". (笑)

何　With ninben, a person, it's なに　nani, what, or a counter. Henshall says this used to be about bearing a load, maybe but now is purely phonetic in Japanese usage.

苛 Under grass crown (草冠), it's teasing, tormenting, persecuting, scolding (いじ・める、さいな・む、いらだ・つ、から・い、つまか・い); Henshall seems not to have an entry for it, though it's 常用 jouyou, among the daily-use kanji taught in schools. (Interesting: Jisho says that one of the parts of this kanji is 艾, Japanese mugwort. 何?!　I image-searched 艾 and found this weird drawing of someone burning someone's arm with some kind of cigar.)

荷 With ninben under grass crown, it becomes a burden (に　ni, the ni in nimotsu, baggage, 荷物 = burden-thing—though motsu with a different kanji is also "to hold". ateji? 荷を持つ。荷物を持つ。荷物を持つのを待つ。)　Henshall says its origins are obscure but, since there's still a minor association in China with the lotus, it may have had something to do with the large head of the lotus. I'm going to say it's a person walking by the river with a huge bundle of grass/hay (or mugwort) on his head. Or maybe it's back to that idea of permission/ability for 可; maybe the person is able to carry a bunch of grass on his head.

And there are some more sugiru-like kanji that also carry the reading of カ, though in this case the radical seems to be more about vertebrae:

過 With "movement/road" in the hen position, it's passing, surpassing, exceeding, perhaps as in an error (すぎる). Henshall says the tsukuri involves vertebrae and ease of movement and carried a meaning of "substantial".

渦 With three drops of water (三水), it's uzu, a swirl, whirlpool, eddy. Henshall says this actually used to contain 之繞, the same "advancing" radical as in 過, and that the kanji once suggested water that moved flexibly, like a spine.

禍 With an altar/holiness, it's a calamity or disaster. Henshall says the "backbone" tsukuri part here expressed rebuke, though that's a bit confusing if 可 had a meaning of approval/possibility. So, a disaster as a rebuke from the gods. Excellent reading of わざわい wazawai. It shares the reading and the meaning with the very awesome kanji 災, combining flood and fire.

For fun, I looked up vertebra/backbone to see what kanji is actually used. Jisho says 脊椎骨 / seki/tsui/kotsu, with se as height or the (anatomical) back and KOTSU as hone, a bone (with our friend the vertebral radical plus tsuki 月, which is the moon but also flesh. TSUI, weirdly enough, is a beech tree. Would make more sense, maybe, if it were a birch tree.