Why did my equations not change font?

Handwriting font packages replace text fonts only. Math is typeset from a separate set of math fonts, and almost no handwriting font ships one. Anything inside dollar signs keeps the default Computer Modern math face. This is correct behaviour, not a bug. For script-style math use the rsfs or euscript packages, which provide uppercase script letters for mathcal and mathscr.

How do I use the xkcd font in LaTeX?

Humor Sans, the font used in xkcd and in matplotlib's xkcd style, is not in TeX Live. Install the TTF on your system, compile with XeLaTeX or LuaLaTeX, and select it with fontspec using setmainfont. pdfLaTeX cannot load a system TTF directly.

Do handwriting fonts support accented characters?

Depends on the package. The ones built for T1 encoding, such as aurical, cover the accented Latin range. METAFONT-era fonts in OT1 often do not, and a missing glyph shows as a warning and a blank. Load fontenc with T1 and test the characters you actually need before writing the document.

Can I use a handwriting font for a whole thesis?

You can, and you should not. Most university regulations require a legible standard font and several name specific ones. Handwriting faces are for a dedication page, a facsimile quotation, or an epigraph, not for 200 pages of body text.

LaTeX reference

LaTeX handwriting fonts

Every handwriting and cursive face shipped in TeX Live, what each one actually looks like, and the code to switch. Plus the thing that catches everyone: your equations will not change, and that is correct.

The packages, all of them

These all ship in a full TeX Live or MiKTeX install, so there is nothing to download. If one is missing, tlmgr install <name>.

Package	Style	Notes
augie	Informal American handwriting, upright	Type 1. The default choice if you want something that reads as a person's notes rather than calligraphy.
aurical	Three faces: Auriocus Kalligraphicus, Lukas Svatba, Jana Skrivana	T1 encoding, Type 1, oldstyle digits, machine-generated bold and slanted. The best-covered of the set.
calligra	Peter Vanroose's own hand, sloped	METAFONT source. LaTeX support comes via `fundus-calligra`. See `calligra-type1` for the Type 1 version.
frcursive	French cursive, the joined hand taught in French schools	Looping and formal. Looks wrong for English prose, right for a quotation in French.
twcal	Calligraphic handwriting	Available through `fundus-twcal`.
va	Handwriting	Via `fundus-va`.
la	Children's school handwriting	Via `fundus-la`. Also ships `lla`. Genuinely useful for teaching material.
miama	Miama Nueva, a flowing modern script	Full LaTeX support. The most decorative option here.
brushscr	Brush script	Thick stroke, signwriting feel.
vicentino	Vicentine renaissance calligraphy	Period chancery hand.
schwell	Schwell-style handwriting
aboensis	Late medieval cursive	OpenType, so XeLaTeX or LuaLaTeX.
oesch	Österreichische Schulschrift	Austrian school script.
schulschriften	German school scripts, Sütterlin through to modern	A bundle covering the historical range. The right tool if you are setting German archival material.
tex-gyre-chorus	Extended URW Chancery L	Chancery italic rather than handwriting. Cleaner and more legible at small sizes than most of the above.
lobster2	Lobster Two	Works with all engines. Display script, not a hand.

Source: the CTAN calligraphic font topic. Several of these date from the METAFONT era and have limited character coverage; test the glyphs you need first.

Using one

Most of these follow the same pattern: load the package, then use its switch inside a group so it does not leak into the rest of the document.

\documentclass{article}
\usepackage[T1]{fontenc}   % do this, or accented characters break
\usepackage{calligra}

\begin{document}

Normal body text here.

{\calligra This line is in Calligra.}

\end{document}

For frcursive the switch is \frcursive, and the pattern is identical. Each package's documentation names its own switch; texdoc frcursive from a terminal opens it.

Any system font, including xkcd

The packages above are what TeX Live ships. If you want a specific font that it does not, including Humor Sans (the xkcd face, the one matplotlib's xkcd style uses), the route is XeLaTeX or LuaLaTeX plus fontspec. pdfLaTeX cannot load a system TTF.

% compile with xelatex or lualatex, not pdflatex
\documentclass{article}
\usepackage{fontspec}

\newfontfamily\hand{Humor Sans}        % any font installed on your system
% or set it for the whole document:
% \setmainfont{Humor Sans}

\begin{document}
{\hand This is in Humor Sans.}
\end{document}

The name in braces is the font's family name as your OS reports it, not the filename. On macOS, Font Book shows it. On Linux, fc-list : family | grep -i humor.

Why your equations did not change

This is the question everyone arrives with

You loaded a handwriting package, the prose changed, and everything inside $ ... $ is still Computer Modern. Nothing is broken.

Text fonts and math fonts are separate systems in LaTeX. A text font package replaces the text family only. Almost none of these handwriting faces ship a math font, because building one means drawing integrals, summation signs, delimiters at four sizes, and several hundred symbols. So math falls back to the default, which is the sensible outcome.

If what you actually wanted was script-style letters in math, that is a different package:

\usepackage{mathrsfs}   % \mathscr{ABC}  -- Ralph Smith's Formal Script
\usepackage{euscript}   % \EuScript{ABC} -- Euler Script
% rsfso gives a lighter rsfs-based calligraphic, good for \mathcal

These cover uppercase Latin only, which is the convention anyway: script letters in mathematics are capitals.

When not to use one

Not for a thesis body. University regulations generally require a legible standard typeface and many name specific ones; Harvard's GSAS, for instance, publishes a list of eleven acceptable fonts with required point sizes, and none is a handwriting face. See the per-university thesis format guides for what yours actually permits.

Where these earn their place is small and deliberate: a dedication page, an epigraph, a facsimile of a quoted letter, a figure label meant to look sketched, teaching material where children's script is the point. One page, not two hundred.

Handwriting to LaTeX. The opposite direction. Photograph handwritten math and get LaTeX back.
Convert handwritten math. How to photograph an equation so the recognition holds up.
Thesis format guides by university, including which fonts each one allows.
LaTeX to Word.