Continuity mistake: At the beginning of the fight with the assassin droids, Anakin cuts off the right arm of the one Ahsoka ends up fighting. Yet during the fight, just before she says "Get back, ya pistonhead", the droid briefly has both arms. (00:12:10)
Continuity mistake: Before the clones retake the base, they have just enough blasters between them for all five of them to wield one each. When Rex is dealing with the commando droid captain, his left holster still has a pistol in it even though he loaned his other pistol to Cody. (00:14:00)
Continuity mistake: Wolffe, Sinker and Boost are shown boarding the escape pod twice: first from inside of it and then in the next shot from the pod bay running past Master Plo. (00:03:35)
Continuity mistake: Chopper's eyes are different colours, with his right eye a whitish hue. However, in the close-up of him after he first comes under suspicion, both of his eyes are brown. (00:12:02)
Continuity mistake: When Cody comes out of the turbolift with Slick, he's carrying a plain white helmet instead of his regular customized one. (00:00:49)
Continuity mistake: When Commander Ponds is first seen, running between the AT-TEs travelling along the canyon wall, his kama (kilt) is missing in the second shot of him before reappearing in the next one. (00:01:22)
Continuity mistake: When the three Jedi Cruisers are shown after a vulture droid crashes into the Resolute's bridge, the one on the left, the Defender, has had one of its two bridges destroyed. After a cut to a different shot, the next shot of the three ships as they turn to retreat has the Defender with both bridges intact. (00:06:28)
Continuity mistake: During Dooku's conversation with Sidious, he's wearing his cape. When Dooku stands up as Ventress enters the room afterwards, his cape has abruptly disappeared.
Continuity mistake: Ahsoka escapes from General Grievous by cutting his right hand off. When Grievous jumps into his starfighter, he suddenly has his hand back. (00:18:11)
Continuity mistake: When Ahsoka asks R3-S6 how the droid's first adventure was and Anakin snaps that he thinks he's lucky to be alive, Anakin's clothes below his belt are missing the black overtunic, leaving only the red tunic below it. (00:20:17)
Continuity mistake: When Rex starts giving the rookies a pep talk, as well as in the shot afterwards where all the clones grab their helmets, Echo's helmet is missing the binocular attachment. (00:16:28)
Continuity mistake: At the beginning of the briefing about the visit to Florrum, Rex's kama (kilt) is missing. (00:15:49)
Continuity mistake: When Grievous calls a battle droid who asks if the Rishi station's destruction was a good thing an idiot, the clasp of his cloak is missing. (00:21:15)
Continuity mistake: When Obi-Wan says, "Unlike you, maybe he's getting some much-needed rest," he's stroking his chin with his hand. Mid-sentence, the scene cuts to a closer shot of Obi-Wan, and his hand changes position. (00:02:50)
Jedi Crash - S1-E13
Continuity mistake: Anakin sends a ship to dock with Aayla Secura's stricken Jedi Cruiser to pick up everyone who's escaping. When the ship arrives, there are two clone pilots flying it. When Commander Bly gets to the bridge to turn on the deflector shields, one of the pilots has vanished. (00:04:52)
Continuity mistake: Rex climbs onto a barrier of pods that the Jedi built in front of the village to take a look at the approaching droid forces and reports that they have eight minutes tops before the Separatists' arrival, prompting Anakin to order the shield generators put in place. Cut to General Lok Durd and his chief battle droid, who look through binoculars at the distant village, where the barrier is shown as incomplete, with Ahsoka and Aayla still moving pods into place. (00:15:45)
Continuity mistake: After landing the Separatist shuttle at the Lurmen village, Anakin, Ahsoka and Aayla get out and walk around the shuttle, underneath its legs, toward Tee Watt Kaa and Wag Too, as Aayla announces that the Separatists will arrive in moments. When she's finished speaking, the three Jedi have emerged from underneath the ship. The scene cuts to Tee Watt Kaa demanding to know why they came back, and when the scene cuts back to a close-up of the three Jedi, they're walking out from underneath the shuttle again. (00:14:40)
Jedi Crash - S1-E13
Continuity mistake: When the Jedi's ship is in danger of crashing into a star while in hyperspace, there is a brief shot where Rex's kama (kilt) is missing, while Ahsoka is arguing with Aayla about shutting down the ship's power. (00:07:05)
Continuity mistake: When Anakin and his men rush to aid Obi-Wan in the south tower, about half a dozen droids marching inside separate the two Jedi. Anakin begins cutting them up; one of the droids is already crossing the threshold. But when Anakin finally reaches Obi-Wan, the droid who has already entered is suddenly no longer present. The hips and legs falling in before Anakin rushes in come from another droid just outside the door.
Answer: Dooku never accepted Ventress as his apprentice, as far as I know; he just kept her as his devoted personal assassin. In Phantom Menace, it is stated that there can be only two Sith at a time, to prevent a power struggle in the lower ranks. To accept Ventress as an apprentice, Dooku would have violated that rule.