Dance like an eggplant!
Steals away EXP? When you switch one Pokémon for another, they all gain full EXP. It hasn't been halved since Generation IV.
The thing about doing that is that it takes longer as you have to switch one Pokemon in and then back out again the next turn which isn't worth doing as you could possibly KO 2 Chansey in the time it takes to switch out meaning you won't be getting any more EXP in the long run. Not to mention the Chansey know Heal Pulse which can be annoying if they heal each other when you switch meaning you have to waste another turn lowering one's HP.