In one aspect, the invention relates to substituted 5-aminothieno[2,3-c]pyridazine-6-carboxamide analogs, derivatives thereof, and related compounds, which are useful as positive allosteric modulators of the muscarinic acetylcholine receptor M4 (mAChR M4); synthesis methods for making the compounds; pharmaceutical compositions comprising the compounds; and methods of treating neurological and psychiatric disorders associated with muscarinic acetylcholine receptor dysfunction using the compounds and compositions. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.