For more high quality mashups, check my alt https://www.youtube.com/channel/UCV-wS9TSTo5vXHsLsumz91Q

Sources:
"Assman - Return of the FUCKer (Boss Battle)" by ytpguy https://www.youtube.com/watch?v=HQ5fFqGfS-M
"REVENGE OF KOOLAIDMAN" by Robbi https://www.youtube.com/watch?v=Z6IKKzN4lOM
"Ashman Return of The PizzaBrady with sega and uzya" by Mascient https://www.youtube.com/watch?v=WMApEGXu9Lc

BGM: Batman: Return of the Joker - Boss Theme https://www.youtube.com/watch?v=DlaUzjpBeAA