Sorry for the spoilers, but I can't review this without them. Before turning to the spoilers, let me just say that the storyline had great potential and the comedy was a strong feature, but somewhere in the middle, everything changed, storylines and hints regarding romantic developments were given but not finished and the comedy and several characters close to disappeared, leaving a boring romance lacking chemistry between the leads.

Spoilers start:
The storyline was very bad. It started very good with an interesting male lead (which turned out not to be the male lead after all) who had actual chemistry with the female lead, then suddenly time travel and his own father came into the mix. I was a bit disappointed about that, as I hoped the show to be a realistic one (hadn't read the synopsis). Nevertheless, the comedy was scaled up though and the new male character was refreshing and fun. Things got screwed up though when they changed the leads! They had the nerve to have the father steal the big love of his own son! The son became a barely seen side character and the love of his life started a very boring relationship with his father. The father changed from major comedy element to boring, serious, romantic type, who secretly wooed his son's major crush (not telling his son that he started working at the same company as the female lead, not giving his son a fair chance to compete, doing things for the girl whilst claiming to help his son get her, when all he did was improve his own chances and not helping him in the slightest). The story could have been good if the father had actually helped everyone (help his son and Drill to better dance and perform, helping them get over stage fright and such, help his son get the girl he loves, help his former friend and costar get over his neglected and underrated feelings, etc.) The show was a big disappointment.

The time travel element became even weirder, as I wanted the father to return and die as he was supposed to, making amends to the bad storyline and allowing his son to get the girl after all, but suddenly there were two of him in the past?!?

MJ was also an underdeveloped storyline. In several episodes, he was even hinted to be a contestant for the female lead but suddenly this idea was ditched and when MJ picked up his phone at the rooftop at the end of an episode, the next episode did not even go back to that scene. Like it never happened and was of no importance at all. I even double-checked if I had accidentally skipped an episode, but they just left it hanging... No idea why the writers were starting hints of storylines, but not finishing them. Like the female lead having a very clear dream of wanting to become a civil servant, studying for that throughout the entire show, and in the end working in the entertainment industry as they bluntly inserted a weird story that she had been in a band and wrote songs. Where the hell did that come from!?! It looks like every episode was written on a whim and without context. Very bad writing of what could have been a briliant show and storyline, had they kept up with the comedy and used the father as a helping hand and comedic relief instead of a girlfriend snatcher.