A JavaScript Library to convert text in various useless but amusing ways.
˙sʎɐʍ ɓuısnɯɐ ʇnq ssǝlǝsn snoıɹɐʌ uı ʇxǝʇ ʇɹǝʌuoɔ oʇ ʎɹɐɹqı˥ ʇdıɹɔSɐʌɐſ ∀

Extracted from lunicode.com.

If it looks weird and boxy, you need a Unicode font:

• DejaVu Sans
• Code2000
• GNU Unifont
• Kedage

Use it like this:

// Get the Lunicode object, initializing the effects
var luni = new Lunicode();

// Or if you installed lunicode via npm:
var luni = require("Lunicode");

// Encode text. Use one of the effects shown below. Here it's "flip"
var encodedText = luni.tools.flip.encode("Hello World");  // plɹoM ollǝH

// Decode text back to plain ASCII (or reverse encoding)
var plainText = luni.tools.mirror.decode("ƚxɘT ɿoɿɿiM");  // Mirror Text

// Creepify has a few options. Set them before encoding:
luni.tools.creepify.options.top = true; 	// add diacritics on top. Default: true 
luni.tools.creepify.options.middle = true;	// add diacritics in the middle. Default: true 
luni.tools.creepify.options.bottom = true;	// add diacritics on the bottom. Default: true
luni.tools.creepify.options.maxHeight = 15; // How many diacritic marks shall we put on top/bottom? Default: 15
luni.tools.creepify.options.randomization = 100; // 0-100%. maxHeight 100 and randomization 20%: the height goes from 80 to 100. randomization 70%: height goes from 30 to 100. Default: 100

// To convert Unicode text to HTML, use luni.getHTML(text);
// Also converts \n to <br>\n and multiple spaces to &nbsp; &nbsp; &nbsp; ...
var html = luni.getHTML("ǝpoɔıu∩̤"); // &#x1dd;&#x70;&#x6f;&#x254;&#x131;&#x75;&#x2229;&#x324;

Flips/Rotates text, including numbers (12345) and some special characters: äöü éáú ÄÖÜ ß ô

o̮ ᙠ ∩̤O̤∀̤ n̗ɐ̗ǝ̗ n̤o̤ɐ̤ :sɹǝʇɔɐɹɐɥɔ lɐıɔǝds ǝɯos puɐ (ގㄣƐᄅ⇂) sɹǝqɯnu ɓuıpnlɔuı 'ʇxǝʇ sǝʇɐʇoᴚ/sdılℲ

Mirrors text horizontally. äöü ß èàù. Käseküchlein.

.ᴎiɘ|ʜɔüʞɘꙅɒ̈⋊ .úɒ́ɘ́ ᙠ üöɒ̈ .ʏ||ɒƚᴎoƹiɿoʜ ƚxɘƚ ꙅɿoɿɿiM

Adds
diacritics

Ą̵̛͎̗͎̯͕̺̭͍̩͐̄̄͗̿͛̔̀́̋̄͜d̷̨͉͇̞̲̥͈̝̺̘̪̥̟͚̘̫̑̋̎͜͜ḑ̵̡̛̤̱̣̼̞̥̻͕͗̔̀̐́̆̐̓͌̊͛̐̉̚͝s̴̯̤̓̐͒̓̉͆̿̔̚͝ ̶̭̼͂̃d̴̡̰̯̲̣̘͉͉̯̣̥͋̈́̊̏̓̀͒̚i̷̮̭͋̈́̋͋̉͊̄̓͂̕a̶̳̣̲̓̊͋c̵̡̛̗͕̖̻͇̪͆̌͒͊͛͌̽̐̇̇̀͊̂̈͒̚͜͠ṙ̷̡̹̱̜̖̦̭ĩ̵͍̪̘͚̗̰͓̙͛͆̽̾͒̏̀͗̊̊́̍̉͒̊ţ̶̙͙̙͉̱́̀̈́̿͛͊̎̓̉̕̕͜͝i̵̛̞̭̭̮̱̬̯̙̖̺̼͑͛ͅć̶̢̡̫̻̪̩̤̱̠̰̹̙͒́̀͐͐̚̚͘͝͝ṩ̸̢̧̠͖̩͚̯̳͓̻̪̻̞

Bubbles around normal characters. Uses combining characters for everything else.

Ⓑⓤⓑⓑⓛⓔⓢ ⓐⓡⓞⓤⓝⓓ ⓝⓞⓡⓜⓐⓛ ⓒⓗⓐⓡⓐⓒⓣⓔⓡⓢ   .⃝ Ⓤⓢⓔⓢ ⓒⓞⓜⓑⓘⓝⓘⓝⓖ ⓒⓗⓐⓡⓐⓒⓣⓔⓡⓢ ⓕⓞⓡ ⓔⓥⓔⓡⓨⓣⓗⓘⓝⓖ ⓔⓛⓢⓔ   .⃝

Squares, via combining characters.

S⃞   q⃞   u⃞   a⃞   r⃞   e⃞   s⃞   ,⃞    v⃞   i⃞   a⃞    c⃞   o⃞   m⃞   b⃞   i⃞   n⃞   i⃞   n⃞   g⃞    c⃞   h⃞   a⃞   r⃞   a⃞   c⃞   t⃞   e⃞   r⃞   s⃞   .⃞

Round squares, via combining characters.

R⃣ o⃣ u⃣ n⃣ d⃣ s⃣ q⃣ u⃣ a⃣ r⃣ e⃣ s⃣ ,⃣ v⃣ i⃣ a⃣ c⃣ o⃣ m⃣ b⃣ i⃣ n⃣ i⃣ n⃣ g⃣ c⃣ h⃣ a⃣ r⃣ a⃣ c⃣ t⃣ e⃣ r⃣ s⃣ .⃣

Wonky alternatives to the usual characters.

చօղҟվ ąӀէҽɾղąէìѵҽʂ էօ էհҽ մʂմąӀ çհąɾąçէҽɾʂ.

Tiny Capitals.

ᴛɪɴʏ ᴄᴀᴘɪᴛᴀʟꜱ.

• FileFormat.info - The best Unicode reference
• Wikipedia: Transformation of Text - Table for flipped characters and others infos
• reddit.com/r/unicode - The webs biggest unicode-for-fun community (needs more members)
• David Fadens Flip - Initial inspiration and characters
• Thomas Schilds upsidedown.info - Inspiration and comparison
• Macchiato - Mirrored ASCII - Initial codepoints for mirrored text
• Alan Wood’s Unicode Resources - Codepoints for Bubble Text
• Wikipedia: Combining Character - For Creepify, Upsidedown Umlauts, Squares, ...
• Michael Kaplan's "What do you get when you combine a base character with a buttload of diacritics?" - Idea for creepify
• Unicode emoticons, Collection of unicode faces and Unicode smileys
• funicode.com - Idea and lower case characters for Bent