Heya!
I most certainly did place a number of fanart pieces in my portfolio! I have some Warcraft, Marvel, and Sega character pieces along side original art.
I wouldn’t fill a portfolio with only fanart, but fanart itself is not a bad thing! If you’re proud of it, show it! You’re still demonstrating your color, compositions and anatomy and attention to details, but fanart can also be used to demonstrate that you can work well with an established IP (intellectual property).
Ahhh thank you for the thoughtful answer! I have some fanart pieces I’m super proud of and was unsure if I should include them or not. Thank you!