El Alagui broke the deadlock for the Bees just before the break, firing home Norris' left-wing cross on the half volley.
The hosts extended their lead straight after the restart, which brought three goals in a breathless six minutes.
Norris drilled home after a defence-splitting through ball from substitute Jake Reeves before El Alagui rounded the keeper to score from the tightest of angles.
But Wimbledon responded on 56 minutes when Fenlon smashed home a 20-yard screamer minutes after George Porter saw his goal-bound effort cleared off the line.
It was only a brief respite, with on-loan Cardiff defender Nugent powering home a header from Saunders' cross and ex-Villareal veteran Venta slotting home after Norris' close-range strike was blocked.
Wimbledon finished strongly, Francomb finishing a slick five-man move eight minutes from the end and Sweeney making it three when he converted Porter's low cross.
- George Francomb
- Luke Norris
- Farid El Alagui
- Jim Fenlon
- Ben Nugent
- Peter Sweeney