Ken Akamatsu, the manga author, appeared in episode 14 of the TV series and in both the Christmas and Spring specials as a plot device and for comic relief. He is referred to in the movies as "Akamatsu-sensei". He is referenced in episode 14, where everyone in the Hinata Inn has to work for 10,000 yen. Keitaro works for him as a manga inker, but eventually leaves, and becomes broke, forcing Keitaro to return to Akamatsu. In the Christmas Special, he helps Kitsune and Shinobu with their financial problems by making them sell his books. In the Spring Special, he is forced to take Motoko, Mutsumi, and Kitsune on his yacht (and when he was about to go on vacation too!).

In connection with Ken Akamatsu, characters from his A.I. Love You manga make the most minimal cameo appearance in the Love Hina anime. A picture of Saati and Hitoshi is shown on the side of Akamatsu's yacht in the Spring Special. Also, the manga Keitaro is inking in episode 14 is A.I. Love You, as it has a very distinct picture of Toni. Also, the books that Kitsune and Shinobu sell in the Christmas Special are A.I. Love You.

Keitaro and Ken Akamatsu look very similar, especially when drawn in chibi form.

(Source: Wikipedia)