Alphys is the Admiral of the Royal Navy, and a major character encountered in TS!Underswap.
Alphys is a yellow lizard monster, wearing a dark blue uniform with golden shoulder pads. She has a scar on her closed left eye, and a monocle under the right.
While not much is known regarding her personality, it has been stated that Alphys delivers powerful speeches to the residents of Crystal Springs.  However, it may be the case that these speeches are as much to herself, as they are to the public--indicating that she still suffers from low confidence issues. 
Alphys first appears in Crystal Springs.
- Alphys knows about Sans's "hobby" as Crossbones, sometimes to her displeasure, as he acts independently of the Royal Navy. However, the two are still friends. 
- This is somewhat ironic, as Undertale Undyne does not want Papyrus in the Royal Guard, while TS!Underswap Alphys wishes for Sans to join the Royal Navy, most likely because he is more capable of handling the task.
- Alphys appears to have an accent, possibly French or German.
- It has been shown that Alphys helped design Sans's Crossbones costume.
- Alphys is the Admiral of the Royal Navy, delivering powerful speeches to the residents of Crystal Springs. - Official TS!Underswap Tumblr
- Alphys' speeches are as much to herself as to the public. - Official TS!Underswap Tumblr
- She’s still friends with Sans, though, and knows about his little “hobby.” - Official TS!Underswap Tumblr