This work investigated the fixed-time consensus (FxTC) tracking problem for nonlinear multi-agent systems (MASs), considering input delay and external disturbances, via an event-triggered (ET) mechanism under undirected fixed and switching topologies. To begin with, a novel ET controller was designed. Its distinctive feature is the inclusion of the constant delay term and compensation terms, which is different from the existing protocols. Consequently, it provides designers with flexible options for practical implementations in the context of time-delay systems subject to external disturbances. Through this approach, under fixed topology, all follower agents were able to achieve FxTC tracking, and importantly, a settling time (ST) upper bound was directly computed by using the system's predetermined parameters. Furthermore, it was rigorously proven that Zeno behavior was excluded. Then, those results were extended to switching topologies. The presented controller guarantees FxTC while significantly reducing both its update frequency and the overall energy consumption of the system. Finally, simulation examples were carried out to demonstrate the validity of proposed findings.