What are YOUUUUUU doing here?!!?
Andrew Luck returned to Colts headquarters in Indianapolis on Thursday -- the first time we've seen him back there since retiring in August ... and he looks happy!
The QB hung up his cleats right before the regular season kicked off, explaining he couldn't handle any more physical abuse.
Of course, Jacoby Brissett took over as QB1 and he's been doing pretty well so far ... the Colts are 3-2 and coming off a huge upset victory over the K.C. Chiefs.
The Colts are on a bye this week -- but a bunch of players were still at the facility on Thursday including T.