During season three, Ken Marino from The State made an appearance. He's best known for his character Louie, The Guy Who Says His Catch Phrase Over and Over Again. After successfully cock-blocking him, Hank tells him to make a cup of tea and "dip his balls in it".
Mia, whose age of 16 is an important plot point, is played by an actress who is in her early 20s, and visibly so. The fact that she looks much older is also an important plot point. It also doesn't help that Madeline Zima is 5'8".
Averted with Madeleine Martin (Becca), notable given this show is NOT kid friendly.
Genius Bonus: The show is filled with classic rock and heavy metal references. In fact, Hank's books South of Heaven, Seasons in the Abyss, and God Hates Us All are named after albums from American thrash metal band Slayer.
Ever wanted to see Lara Croft naked? Here's the code: check out season 5 of Californication. (Marcy and Stu's British nanny was played by Camilla Luddington, the voice of Lara in the 2013 Tomb Raider reboot.)