[Splat]

No, Carl can't be alive! In fact, that wasn't even Carl! It was, uh, a member of the Carl Internet Cult in a Carl costume! Yeah!

Actually it was a one panel joke caused by a time anomaly resulting from continuum ripples caused by the strength of the global nuclear detonation UltraSafe set off at the end of WOTA 2. Carl randomly disappeared from his prison cell prior even to Dennis's missile plot and briefly appeared in UltraSafe's bunker just in time to be the six hundred and sixty sixth interviewee in his henchling hunt, before time realigned itself and he was returned to his former timeline.