  Understanding of the so-called 2 particle-2 hole (2p-2h) effect is an urgent
program in neutrino interaction physics for current and future oscillation
experiments. Such processes are believed to be responsible for the event
excesses observed by recent neutrino experiments. The 2p-2h effect is dominated
by the meson exchange current (MEC), and is accompanied by a 2-nucleon emission
from the primary vertex, instead of a single nucleon emission from the
charged-current quasi-elastic (CCQE) interaction.
  Current and future high resolution experiments can potentially nail down this
effect. For this reason, there are world wide efforts to model and implement
this process in neutrino interaction simulations. In these proceedings, I would
like to describe how this channel is modeled in neutrino interaction
generators.
