"What's it taste like?"
"It's hard to say, Bo. Kind of spoo-ish, I guess."
- – Mack
Mack was a maintenance worker on Babylon 5.
In 2262, he was partnered with Bo and the pair served as an on-call "floater" team. They were witnesses to several key elements of the stations defensive efforts against an unknown alien race. Throughout these events, Mack and Bo were called upon to perform key maintenance tasks, including in C&C.
While Bo repaired medlab, Mack was in C&C repairing the secondary targeting console just in time to destroy one of the enemy ships. Mack then met up with Bo in the fighter bay.
The pair were briefly caught in the melee between the alien boarding party and security, forced to defend themselves; Mack made use of a discarded PPG rifle to kill one of the attackers while Bo engaged in fisticuffs. Fleeing the skirmish they encountered Byron's telepaths, who permitted them to stay. Mack was clearly nervous being around them, even more so when the telepaths used their abilities to briefly control an intruder and force them to leave. Mack therefore hurried to leave and was clearly discomforted by Bo's decision to engage Byron in conversation, even more so when (at Bo's unwitting prompting) Byron briefly projected Bo's mind into that of one of the Starfury pilots of whom Bo had expressed admiration. Apparently unaware that Bo felt gratitude for that act, Mack hastily left when Byron stopped, forcing Bo to follow him.
While heading to perform new maintenance duties they were stopped by President Sheridan himself, who told them to escort Delenn to the lifepods safely, irrespective of their assigned duties. On the way, Delenn stopped and engaged them in conversation, surprising Mack, who admitted the "big" people rarely noticed them, never mind ask their names or talk to them as Delenn was doing. Delenn convinced Mack and Bo that if she was forced to enter the lifepod, she would smash the equipment rendering a safe landing impossible and convinced them to let her stay on the station. Mack went on to state how beautiful he felt her smile was.
Almost immediately afterwards, Mack discovered and revealed to Bo the arrival of help in the form of the White Star fleet. He and Bo ruminated on the burdens upon them and agreed that if the command staff can endure their burdens, then they can deal with theirs. Mack briefly complained that the pilots and soldiers got all the glory, but was silenced by the sight of Franklin inspecting the bodies of the dead.
Upon visiting C&C again, Mack hesitantly informed Lochley that she was "okay in my book," for which Lochley thanked him. Heading off, he and Bo passed Sheridan and Delenn, who greeted them by name as she passed, which got Mack's attention and he expressed a brief interest in her. After this, he and Bo headed off to lunch.