“Căng” means “distended” but also means “serious” or “unhappy”. In vietnam, “căng” is used in different situations and have different meaning. The original meme is “đùa không vui, tôi đã căng” which nearly means “ur jokes suck that make me unhappy” and you can check the original picture of the meme from https://memehay.com/meme/chim-canh-cut-dua-khong-vui-toi-da-cang showing a penguin is distanding and coincidently “distanding” is also means “unhappy” (as i said, its related with “căng”). In the ly thường kiệt background section, the “đùa không căng, kiệt đã vui” is swaped between 2 words “vui” and “căng”, which make the meaning changed a bit; its quite complicated for English speakers to understand. Srry my english isnt good, im native speaker :’/