Ｔｈｅ ｑｕｉｃｋ ｂｒｏｗｎ ｆｏｘ ｊｕｍｐｓ ｏｖｅｒ ｔｈｅ ｌａｚｙ ｄｏｇ
𝐓𝐡𝐞 𝐪𝐮𝐢𝐜𝐤 𝐛𝐫𝐨𝐰𝐧 𝐟𝐨𝐱 𝐣𝐮𝐦𝐩𝐬 𝐨𝐯𝐞𝐫 𝐭𝐡𝐞 𝐥𝐚𝐳𝐲 𝐝𝐨𝐠
𝕿𝖍𝖊 𝖖𝖚𝖎𝖈𝖐 𝖇𝖗𝖔𝖜𝖓 𝖋𝖔𝖝 𝖏𝖚𝖒𝖕𝖘 𝖔𝖛𝖊𝖗 𝖙𝖍𝖊 𝖑𝖆𝖟𝖞 𝖉𝖔𝖌
𝑻𝒉𝒆 𝒒𝒖𝒊𝒄𝒌 𝒃𝒓𝒐𝒘𝒏 𝒇𝒐𝒙 𝒋𝒖𝒎𝒑𝒔 𝒐𝒗𝒆𝒓 𝒕𝒉𝒆 𝒍𝒂𝒛𝒚 𝒅𝒐𝒈
𝓣𝓱𝓮 𝓺𝓾𝓲𝓬𝓴 𝓫𝓻𝓸𝔀𝓷 𝓯𝓸𝔁 𝓳𝓾𝓶𝓹𝓼 𝓸𝓿𝓮𝓻 𝓽𝓱𝓮 𝓵𝓪𝔃𝔂 𝓭𝓸𝓰
𝕋𝕙𝕖 𝕢𝕦𝕚𝕔𝕜 𝕓𝕣𝕠𝕨𝕟 𝕗𝕠𝕩 𝕛𝕦𝕞𝕡𝕤 𝕠𝕧𝕖𝕣 𝕥𝕙𝕖 𝕝𝕒𝕫𝕪 𝕕𝕠𝕘
𝚃𝚑𝚎 𝚚𝚞𝚒𝚌𝚔 𝚋𝚛𝚘𝚠𝚗 𝚏𝚘𝚡 𝚓𝚞𝚖𝚙𝚜 𝚘𝚟𝚎𝚛 𝚝𝚑𝚎 𝚕𝚊𝚣𝚢 𝚍𝚘𝚐
⒯⒣⒠ ⒬⒰⒤⒞⒦ ⒝⒭⒪⒲⒩ ⒡⒪⒳ ⒥⒰⒨⒫⒮ ⒪⒱⒠⒭ ⒯⒣⒠ ⒧⒜⒵⒴ ⒟⒪⒢
Bing doesn't understand any, if you search it, the first result is the github repo with these frases.
Necessarily then, there should not be other sets that encode things you can't in Unicode, since then you can't displace those with Unicode.
So, particularly in the early life of Unicode the goal was collect stuff that already exists and add it to Unicode. (These days we're finished with that and most new work is on adding things that weren't previously in any character set)
Two controversial things were done, at opposite ends of the spectrum, during this period of consolidation:
What you're seeing here is adding copies of the entire Latin alphabet, but with some particular property that Latin users would not really consider part of the character, such as "bold" or "italic" but which _was_ preserved in some character set being used somewhere. Without this choice, if we converted a text file encoded in a way that distinguished bold and italic characters, we'd lose that bold/ italic and it might be significant. This would be like when you get a black & white photocopy of a sheet that says
"Ignore any text below shown in red"
Um, but none of this text is red? Oh. Probably some of it was before it was photocopied. Oops.
At the far end of the spectrum, a process called CJK unification took place in which scholars of the languages using characters from the Han ("Chinese") writing system decided that although say, a Japanese character set and a Chinese character set both had a particular character, and the Chinese and Japanese would not draw this character the same way, actually in some linguistic sense it's the same character (and in many cases the visual differences are quite small) and so Unicode should not encode both separately.
There's a coherent technical argument for why both these types of decisions made sense, but they were nonetheless controversial.
You should not use weird characters like italic Latin letters in new documents, but you also should not transform these characters without warning when processing an existing document as you may lose important meaning.
Both had always bothered me deeply, but I'd never stopped to think that they're also essentially opposed in philosophy to each other. So now that I'm aware of that, I'm triply annoyed :S
The first line, Ｔｈｅ ｑｕｉｃｋ ｂｒｏｗｎ ｆｏｘ, originates with east-Asian character based terminals, on which ideographic characters occupied twice the space of alphabetic characters, and there was also a desire to have latin characters that were also double width. See https://en.wikipedia.org/wiki/Halfwidth_and_fullwidth_forms
The middle lines are included as mathematical symbols. The justification is that 𝑖 is a mathematical symbol that has its own independent meaning, which only coincidentally looks like italicized i. (I think this is silly, and naturally leads to a bloody mess as people misuse these symbols as letters, and in this case there is no backwards-compatbility excuse.) https://en.wikipedia.org/wiki/Mathematical_Alphanumeric_Symb...
The final line, like the first, is apparently present for compatibility with pre-Unicode east-Asian character sets. https://en.wikipedia.org/wiki/Enclosed_Alphanumerics