Well, I do my own as well... kinda hard to find some...
Asriel (Undertale) to Els (Beastars)
Ori (Ori And the blind Forest) to Fidget (Dust: An Elysian Tail)
Ruffnut Thornton (How do you Train Your Dragon) to Alibaba (Magi)
Fran Bow to John Darling (Peter Pan_Disney)
Campanella (Night on the Galactic Railroad) to Liona (Paddle Pop/Max Adventures)
Yugo (Wakfu) to Rin Kagamine (Vocaloid)
Honoka Yukishiro (Futari wa Pretty Cure) to Rentaro Satomi (Black Bullet)
and no Kanji gender swap. Slimes are genderless creatures.
Sheila Levitt (Terra Formars) to Saton Kazuma (Konosuba) // Gylfie (Guardians of Ga’Hoole) to Master Hu (Peggle Nights)
Zoe Elgin (Xombie) to Hanzo Urishihara -Lucifer- (Hataraku Maou-sama)
Noah Kaiba (YugiOh!) to Summer Wallflower (Equestria Girls)
Professors:
Frank West (Dead Rising) to Roberta (Black Lagoon)
Rose (Plants vos Zombies) to King Ziar (Fran Bow)
Extras:
Ophelia (Brütal Legend) to The Baron (Brütal Legend)
Scarecrow (Oz: Broken Kingdom) to The Scarecrow (Creepypasta)
Tomie Kawakami (Junji Ito’s collection) to Amos Valdogoad (Misfits of a Demon Lord)
New Students:
Letty (Dragon ie kou?) / Stephan (Pokemon) to Alextrassa (WoW) /Atlas (Megaman ZX Advent)
Iruma Suzuki (Mairimashite! Iruma-kun) to Kurumu Korono (Rosario + Vampire)
Aya Asagiri (Mahou Shoujo Site) to Kusaka Kabane (Kemono Jihen)