Psych Up is a status-affecting Normal-type move; it is TM77, located in Route 16 across the ice patch north of Dragon Tamer Kim in versions 1.03 and beyond.
Psych Up copies all of the target's stat stages and replicates them onto the user (Attack, Defense, Special Attack, Special Defense, Speed, accuracy, and evasion). Psych Up bypasses accuracy checks to always hit, unless the target is in the semi-invulnerable turn of a move such as Dig or Fly. It bypasses Protect, Detect and Spiky Shield.