Normally, I wouldn't like that in a live action comedy (it can be good on the Simpsons), but FOTB's flashbacks are pretty funny. From the way the characters dress to show that they're "young" to incorporating people they know now into the story, it's charming and fun.
I love flashback episodes in most shows, this, Friends, How I Met Your Mother, Simpsons, Futurama and so on.
I think it was Friends that made flashback episodes big
Possibly...I think it was "Lost" that took it to a whole new level, where they became an integral part of the plot itself.
If you're not taking any steps forward, you're not moving at all.