When Sarge, Grif, Simmons, Donut, Caboose, Tucker and Church investigate a temporal distortion, they get pulled into another crazy adventure when they are transported to Equestria as ponies! Teaming up with the Mane six, they are forced to protect the land and themselves from O'Malley, as the evil A.I. has 48 hours to complete his task.
Extra info:
This fanfiction does not take place in any specific period during the RvB timeline, but it most resembles the end of season two. The Reds and Blues are still at Blood Gulch, O'Malley is controlling Doc, Lopez still has his body and is still with red team, Tex is not present. Any fan of RvB can tell you that there is no period in the Red vs Blue timeline when all of these things are true at once, making this an alternate universe fiction. As for MLP canon, this takes place after the season four finale.