I'm not 100% convinced you could call it time travel, but what the hey:
Enchanter waaaay back in 1983 (Infocom text adventure) had a section where you, fearless wizard-type-person, found a series of glass panels which looked into sections of dank dungeon corridor. Every so often an adventurer appeared, wandering lost in that dungeon. You, FWTP, could summon that aventurer and get him to help you in your quest.
The joke was, the adventurer was that exact same avatar that you, clueless teenager, had been playing only a short while prior, for he was fearless-adventurer-type-person, the hero of Zork, the first game in the series. So FWTP, which was you, summons FATP, who was also you, and - which was the bit that killed me - promptly looked at the stuff FWTP was carrying and said [paraphrasing] 'Gee, that looks valuable - I mean, heavy. Sure I can't help you carry that?' Which was even more of a laugh and a half because you, clueless teen, knew damn well that when you were in charge of FATP that was *exactly* what you would have done, and in fact did do - hoover up every least valuable object in sight . . .