Stargate SG-1/Recap/S1 E19 There but For The Grace of God

On what appears to be a routine recon mission, Daniel touches an artifact known as the Quantum Mirror and ends up in an alternate universe version where he never joined the Stargate Program, Sam is a civilian, Teal'c is still Apophis' First Prime since alternate!SG-1 never went to Chulak, Jack is a giant douchebag who obviously didn't undergo the character development he went through in The Movie, Abydos and eventually Chulak are destroyed, and the 'SGC' is the 'SGA'.

Alternate!SGA is promptly invaded and destroyed by the Goa'uld, the alternate versions of SG-1 all die, and due to their sacrifice Daniel makes it back to his reality with vital information: Apophis is planning an invasion of Earth.