Young Frankenstein ending explained (spoilers)

[cassandra]

Fredrick gives the Monster half his brain. Fredrick and Inga get married. The Monster and Elizabeth get married.

[Kennethzef]

The townspeople go after The Creature (Boris Karloff) because of Marias death. Henry Frankenstein (Colin Clive) confronts the Creature and is knocked out and taken to a windmill. The Creature tosses Henry and he survives. The townspeople burn the mill and it collapses on top of the Creature. Baron Frankenstein (Henrys father) watches over his son while hes recovering and gives a toast to his future grandson.

[Gregory Hunts]

After the band arrive in Mexico for their first big gig, Jons hunger for fame and success breaks the band apart, leaving him and a confused Frank to perform together. Jon, relishing in the bands YouTube and social media success starts with one of his own songs, which is terrible. Franks breaks down due to his shit music.

In a hotel, Jon tries to remove Franks head. Frank runs away and is knocked down by a car. Jon runs after him, finds his shattered head on the ground and is also run down by a car. When Jon awakens in hospital, he starts to try and find Frank.

Eventually he is lead to an address in Kansas, and after mistaking the tree surgeon for Frank, Jon is approached by Franks mother. Frank is stood on the lawn, vacant, finally without his head. We find out from his parents that Frank has suffered a mental illness all his life.

As Franks old band play in a run down bar with no spectators, Frank (having been brought there by Jon, sat back at the bar) approaches them cautiously while they play a sombre Lighthouse Keeper. He tells them, shyly and unable to make eye contact, how nice it is to see them. Clara realises who it is (having never seen Frank without his head). Guitar player Baraque hands him a microphone as he tells them how much he loves your wall (looking at the wall by him). As Frank starts talking and making his obscure observations, the band starts playing. Michael changes his chorus to I love you all. The misfits are united again, if only briefly.

Jon, realising that he is a complete moron, realises how special this group of people are and leaves the bar on his own, knowing what a complete asshole he is/was.