I Won't Let You Sleep Tonight

is episode 12 of the Beelzebub anime.

Following the 2011 Tōhoku earthquake and tsunami, the pre-opening sequence for this episode had been modified to remove scenes suggesting the disaster.

Summary
Beelzebub has been crying all night for the past three nights, which is causing Oga and the whole neighbourhood to get very little sleep. Wanting to stop his night crying to avoid being chased out of their house, the Oga family attempt to play with Beelzebub all day in order to tire him out come nighttime. Despite managing to get him to sleep, Beelzebub still wakes up and cries in the middle of the night. After Oga spends the day dealing with a sleep deprived Tōhōshinki, Hilda brings a toy that calms Beelzebub down, but is even noisier than his crying.

Next episode preview
This next episode preview was produced and aired prior to the 2011 Tōhoku earthquake and tsunami, as the next episode was originally to succeed episode 9 before being postponed because of the provocative nature of the overall series.

Hilda introduces what's happening next week in the series. Oga's Father introduces himself, feeling nervous as it is his first preview. He comments on how he doesn't really have a name even while Furuichi's sister, Honoka, does. He then remembers to introduce the next episode. Hilda tells the viewers to watch the next episode and bids farewell to the viewers. Oga suddenly yells at them quickly to stop.

Characters in order of appearance

 * 1) Tatsumi Oga
 * 2) Beelzebub IV
 * 3) Misaki Oga
 * 4) Hilda
 * 5) Oga's Father
 * 6) Great Demon Lord (flashback)
 * 7) Oga's Mother
 * 8) Takayuki Furuichi
 * 9) Ishiyama High Principal
 * 10) Hajime Kanzaki
 * 11) Takeshi Shiroyama
 * 12) Chiaki Tanimura
 * 13) Aoi Kunieda
 * 14) Nene Ōmori
 * 15) Kōta Kunieda (dream)
 * 16) Tatsuya Himekawa
 * 17) Hidetora Tōjō (dream)
 * 18) Acid Suzuki
 * 19) Alaindelon