Is it possible to remove the Android smileys that replace text strings like ":)"? A friend of mine was wondering if it's possible to remove or replace these smileys entirely, or if they are a native function of the Android operating system that would require tweaks in a custom ROM to get rid of. Question applies to both tagged devices (S3 and Galaxy Nexus).

These are the smileys we are talking about, for reference:
This is a feature of the particular app that you are using. If you are referring to the SMS Messaging app, there are various SMS apps replacements available on Google Play, you can customize the smiley on some SMS replacement apps or disable them entirely.