What about the weird monsters (al miraj, flumph...). How many monsters (rughly) from the original FF are included ?
Here's a list of the Fiend Folio and what is in the 2024 MM highlighted
GREEN.
Aarakocra • Achaierai • Adherer • Aleax • Algoid • Al-mi'raj • Apparition • Assassin bug • Astral searcher • Babbler •
Bat, giant • Berbalang • Blindheim •
Blood hawk • Bloodworm, giant • Bonesnapper • Booka •
Bullywug • Bunyip • Carbuncle • Caryatid column • Caterwaul • Cifal • Clubnek • Coffer corpse • Crabman • Crypt thing • Dakon • Dark creeper • Dark stalker •
Death dog •
Death knight • Demon • Demon, Lolth • Denzelian • Devil • Devil, styx • Devil dog • Dire corby • Disenchanter • Doombat • Dragon, oriental • Dragon, li lung • Dragon, lung wang • Dragon, pan lung • Dragon, shen lung • Dragon, t'ien lung • Dragon, yu lung • Dragonfish • Dune stalker • Elemental princes of evil • Elemental, Cryonax • Elemental, Imix • Elemental, Ogrémoch • Elemental, Olhydra • Elemental, Yan-C-Bin • Elf, drow • Enveloper •
Ettercap • Eye killer • Eye of fear and flame • Firedrake • Firenewt •
Fire snake • Fire toad • Flail snail • Flind •
Flumph • Forlarren • Frost man • Galltrit • Gambado • Garbug • Giant •
Giant, fog • Giant, mountain • Giant strider • Gibberling •
Githyanki •
Githzerai • Goldbug • Gorbel • Gorilla bear •
Grell •
Grimlock • Gryph • Guardian daemon • Guardian familiar • Hellcat • Hoar fox •
Hook horror •
Hornet, giant • Hound of ill omen • Huecuva • Ice lizard • Imorph • Iron cobra • Jaculi • Jermlaine • Kamadan • Kelpie •
Kenku • Khargra • Killmoulis •
Kuo-toa •
Lamia noble • Lava children •
Lizard king • Magnesium spirit • Mantari • Meazel • Meenlock •
Mephit • Mephit, fire • Mephit, lava • Mephit, smoke • Mephit, steam •
Mezzodaemon • Mite • Necrophidius • Needleman • Nilbog • Nonafel • Norker • Nycadaemon •
Ogrillon • Osquip • Pĕnanggalan • Pernicon • Phantom stalker • Poltergeist • Protein polymorph •
Quaggoth •
Quipper • Qullan • Retriever •
Revenant • Rothé • Sandman •
Scarecrow • Screaming devilkin • Shadow demon • Sheet ghoul • Sheet phantom • Shocker •
Skeleton warrior • Skulk •
Slaad • Slaad, blue • Slaad, death • Slaad, green • Slaad, grey • Slaad, red • Slaad, Ssendam • Slaad, Ygorl • Snyad • Spawn of Kyuss • Stunjelly • Sussurus • Svirfneblin • Symbiotic jelly • Tabaxi • Tentamort • Terithran • Thoqqua • Thork • Throat leech • Tiger fly • Tirapheg • Trilloch •
Troll • Troll, giant • Troll, giant two-headed • Troll, ice • Troll, spirit • Tween • Umpleby • Urchin • Vision • Vodyanoi • Volt • Vortex • Whipweed • Witherstench • Witherweed • Xill • Xvart • Yellow musk creeper • Yellow musk zombie
There might be some that I've missed or some under slightly different names (I caught a few of those), but that's what I got. Someone correct me if I've missed any!