How many total slaps were in the Slap Bet storyline?

There were eight total slaps in the Slap Bet storyline.

Marshall initially receives five slaps after Lily rules on the original bet involving Robin's secret. One slap is delivered immediately, while the remaining slaps are distributed across later episodes. Marshall eventually receives three supplementary slaps, bringing the storyline's total to eight.

The slaps are spread across the series rather than occurring in one scene. They include the first slap in “Slap Bet,” later strikes in “Stuff” and “Slapsgiving,” and another in “Slapsgiving 2: Revenge of the Slap.” Two more arrive in “Disaster Averted” after Barney agrees to additional slaps in exchange for relief from his duckie tie.

The seventh slap occurs in “Slapsgiving 3,” where Marshall gives Barney the dramatically named “Slap of a Million Exploding Suns.” The eighth and final slap occurs in “The End of the Aisle,” when Marshall slaps Barney during a panic attack. The common mistake is counting only the original five rather than the complete series storyline.