During my job, I regularly walk into Android sources and, sometime I found funny things in source code.

I found the first one in the build toolchain where all Makefile functions are defined. Do you wanna go out with the Android ? Because he won’t.

.PHONY: out
        @echo "I'm sure you're nice and all, but no thanks."

I found the following one when the multi-users feature appeared in JellyBean (4.1/4.2):

/**
 * Used to determine whether the user making this call is subject to
 * teleportations.
 * @return whether the user making this call is a goat
 */
public boolean isUserAGoat() {
    return false;
}

The funnier aspect is that this method is officially documented here.

[edit 2013-08-22] More funny sources in the well named category 😉