My young son is a big fan of the TV show and I usually get a chuckle out of the goofy family Dexter is forced to deal with, so we grabbed this from the rental shelf to check it out.
The movie is all about Dexter (present and future) and his nemesis, Mandark. There is little of sister DeeDee, and no sign of glove-wearing mom or good old dad. Dexter travels forward in time, then forward still further, then back a little between the first two jumps (I think) in order to meet his future self who he believes "saved the future". He meets and joins up with future versions of himself who are all quite different from present Dexter.
This normally brightly colored cartoon was fairly monochrome in this long feature, and the time jumping was hard to follow a viewer of any age. It lacked the usual characters and laughs of a short episode, but it wasn't meant to be Shrek or anything... (5/10)
BTW - the only part to make me and my son laugh out loud was at the very end when all the Dexter's were saying their farewells... Goodbye Billy! Some more flat out humor and less misery would have been nice.