As Defendants argue, however, Plaintiff's complaint fails to allege any such claim. See, e.g., Elliott v. Strafford County, 2001 WL 274827, at *3 (D.N.H. Feb. 7, 2001) (rejecting Monell claim asserted for the first time at summary judgment stage); see also In re Citigroup, Inc., 2011 WL 1326368, at *2 n. 3 (D.Mass. March 31, 2011) (collecting cases for proposition that “[t]he Court may reject new claims that are not part of a complaint and are instead added for the first time in an opposition to summary judgment or a memorandum in support of a motion for summary judgment”). Nor has Plaintiff moved to amend his complaint to include a failure to supervise claim.