Mysides

3 clues
I'm laughing so much it hurts!
I'm laughing so hard" in memes, and theme of this puzzle
That's hysterical" on the internet, and a hint to this puzzle's theme
Similar answers:
Abides
Abidesby
Acidesther
Adelaideslament
Aides
Aidesdecamp
Aidesforduelers
Alhirtmyself
Allbymyself
Allmysons
Allmysuns
Amides
Amtrakrides
Amys
Amyschumer
Amysharon
Amysmart
Amystudents
Antides
Antiquemystique