MLP G5 is the only mlp generation where a previous pony from the previous generation’s main cast isnt apart of the current generation’s main cast.
G1 and G2 had a sundance (until 1999 when Sundance got her name changed to Sunsparkle)
G2 and G3 had a SweetBerry (until 2008 when G3 main cast was changed)
G3 and G4 had a Rainbow Dash and Pinkie Pie (only generation were 2 ponies from the previous main cast appear as main cast again)